Immunomodulatory minicells and methods of use

ABSTRACT

The present disclosure is related to immunomodulatory bacterial minicells and methods of using the minicells.

RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 14/044,525, filed on Oct. 2, 2013, which claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Application No.61/709,102, filed on Oct. 2, 2012. All of the aforementioned priorityapplications are herein expressly incorporated by reference in theirentireties.

REFERENCE TO SEQUENCE LISTING

The present application is being filed along with a Sequence Listing inelectronic format. The Sequence Listing is provided as a file entitledSEQLISTING.TXT, created Feb. 5, 2016, which is 20 Kb in size. Theinformation in the electronic format of the Sequence Listing isincorporated herein by reference in its entirety.

BACKGROUND

1. Field

The present application is drawn to compositions and methods for theproduction, purification, formulation, and use of immunomodulatoryeubacterial minicells for use in treatment of diseases, such as bladdercancer and other malignancies.

2. Description of the Related Art

The following description of the background of the invention is providedto aid in understanding the invention, but is not admitted to describeor constitute prior art to the invention. The contents of the articles,patents, and patent applications, and all other documents andelectronically available information mentioned or cited in thisapplication, are hereby incorporated by reference in their entirety tothe same extent as if each individual publication was specifically andindividually indicated to be incorporated by reference. Applicantsreserve the right to physically incorporate into this application anyand all materials and information from any such articles, patents,patent applications, or other documents.

It is well known that the immune system plays an important role in theprevention of cancer. It is becoming increasingly clear that immunemodulation may be an attractive therapeutic approach in the treatment ofcancer. The longest standing marketed anticancer immunomodulatorytherapy is a live attenuated strain of Mycobacterium bovis, BacilleCalmette-Guerin (BCG), which is used as a postoperative adjuvant therapyfor the treatment of non-muscle invasive bladder cancer. Othernon-marketed experimental anticancer immunomodulatory approaches includethe use of other live attenuated species of bacteria such as Salmonellatyphimurium, Bifidobacteria, Listeria monocytogenes, Streptococcuspyrogenes, Serratia marcescens, Clostridium novyi, Salmonellacholeraesius, and Vibrio cholera. While somewhat effective, each strainused is limited by the risk of infection, fear of genetic reversion oflive attenuated strains to pathogenicity, and sepsis. All of theseapproaches have been met with extreme toxicity reminiscent of the livingbacterial infection with toxicity occurring at or near the mostefficacious dose. This results in narrow therapeutic indices for eachstrain type.

To address toxicity issues with living bacteria as immunomodulatorytherapy, others have attempted to use different bacterial components (asopposed to the whole living organism) to generate the same immunologicaleffect. Experimental therapeutics of this type include purifiedbacterial toxins, purified pro-inflammatory lipopolysaccharides (LPS),purified teichoic acid (TCA), and other bacterial cell wall preparationsand other bacterial sub-cellular fractions. These approaches haveimproved toxicity profiles but are with a concomitant loss of efficacyin some cases. Additionally, many only stimulate a polarizing immuneresponse (either Th1 or Th2) with the majority stimulating Th2 (antibodygenerating) responses. It is reasonably well documented that a Th1(cellular immune response) response seems to be preferential withrespect to having an anti-tumor immunomodulatory effect. Last, thesepreparations can be difficult to manufacture at a scale and quality tosupport market demand and may only ultimately generate a subset ofimmune responses incapable of generating anti-tumor effects. In the caseof protein toxins used in the treatment of most cancers, efficacy of theprotein toxin is significantly limited by toxicity to normal tissues. Inaddition, drug pharmacokinetic (PK) parameters contributing to systemicexposure levels frequently are not and cannot be fully optimized tosimultaneously maximize anti-tumor activity and minimize side-effects,particularly when the same cellular targets or mechanisms areresponsible for anti-tumor activity and normal tissue toxicity. Again,this results in a very narrow therapeutic index, common for most proteintoxins.

In addition to live bacterial vectors and bacterial components asimmunomodulatory “generalists”, other investigators have attempted todevelop different, specific Th1 immunomodulatory cytokines andchemokines as anticancer therapeutics. Examples include but are notlimited to interferon gamma (IFN-γ), interferon alpha (IFN-α),granulocyte macrophage colony-stimulating factor (GMCSF), tumor necrosisfactor alpha (TNF-α), interleukin-2 (IL-2), interleukin-12 (IL-12), andinterleukin-18 (IL-18). Each of these approaches has been limited byunanticipated and severe toxicity with little or no immunologicaltherapeutic benefit when administered alone. It is becoming somewhatclear that single cytokine or chemokine agents does not invoke the fullspectrum of Th1 immune response needed to have an anticancer effect andthat these factors are likely working in concert at varying levels thatare dynamic over time. This is a nearly impossible cascade ofimmunological signaling events to recapitulate and orchestrate with amultiplex product formulation. Most single agent cytokines have failedclinically, the exception being pegylated interferon for the treatmentof chronic hepatitis C viral infections.

Based on the observed limitations of these approaches to the developmentof immunomodulatory anticancer therapeutics, there is a need for animmunomodulatory therapy that could mimic a live bacterial infectionwithout introducing the risk of infection and infection-associatedtoxicity while still invoking a potent and diverse enough immuneresponse to impart anticancer activity.

SUMMARY

Some embodiments disclose a bacterial minicell, comprising acholesterol-dependent cytolysin protein, wherein said minicell does notdisplay an antibody or other molecule comprising an Fc region of anantibody.

In some embodiments, the cholesterol-dependent cytolysin protein isselected from listeriolysin O, listeriolysin O L461T, listeriolysin OE247M, listeriolysin O D320K, listeriolysin O E247M, listeriolysin OD320K, listeriolysin O L461T, streptolysin O, streptolysin O c,streptolysin O e, sphaericolysin, anthrolysin O, cereolysin,thuringiensilysin O, weihenstephanensilysin, alveolysin, brevilysin,butyriculysin, tetanolysin O, novyilysin, lectinolysin, pneumolysin,mitilysin, pseudopneumolysin, suilysin, intermedilysin, ivanolysin,seeligeriolysin O, vaginolysin, and pyolysin. In some embodiments, thecholesterol-dependent cytolysin protein is perfringolysin O. In someembodiments, the cholesterol-dependent cytolysin protein comprises theamino acid sequence of SEQ ID NO: 1.

In some embodiments, the minicell further comprises invasin. In someembodiments, the minicell does not comprise invasin.

In some embodiments, the minicell further comprises a Th1 cytokine. Insome embodiments, the Th1 cytokine is selected from IL-2, GMCSF,IL-12p40, IL-12p70, IL-18, TNF-α, and IFN-γ.

In some embodiments, the minicell further comprises a Th2 cytokine. Insome embodiments, the Th2 cytokine is selected from IL-1α, IL-1β, IL-4,IL-5, IL-6, IL-10, and IL-13.

In some embodiments, the minicell further comprises a phospholipase. Insome embodiments, the phospholipase is PC-PLC or PI-PLC.

In some embodiments, the minicell comprises a protein toxin selectedfrom fragments A/B of diphtheria toxin, fragment A of diphtheria toxin,anthrax toxins LF and EF, adenylate cyclase toxin, gelonin,botulinolysin B, botulinolysin E3, botulinolysin C, botulinum toxin,cholera toxin, clostridium toxins A, B and alpha, ricin, shiga A toxin,shiga-like A toxin, cholera A toxin, pertussis S1 toxin, Pseudomonasexotoxin A, E. coli heat labile toxin (LTB), melittin, activatedcaspases, pro-caspases, cytokines, chemokines, cell-penetratingpeptides, and combinations thereof.

In some embodiments, the minicell does not comprise any othertherapeutically-active moiety. In some embodiments, the minicell doesnot comprise a therapeutic small molecule, any other therapeuticprotein, or a therapeutic nucleic acid. In some embodiments, theminicell does not display the Fc binding portion of Protein G or ProteinA. In some embodiments, the minicell does not comprise any therapeuticnucleic acid, for example an siRNA.

Some embodiments disclosed herein provide a minicell-producingbacterium, comprising: an expressible gene encoding a minicell-producinggene product that modulates one or more of septum formation, binaryfission, and chromosome segregation; and a recombinant expressioncassette capable of the functional expression of a cholesterol-dependentcytolysin protein, wherein the bacterium does not display an antibody orother molecule comprising an Fc region of an antibody and does notdisplay the Fc binding portion of Protein G or Protein A.

In some embodiments, the minicell-producing bacterium further comprises:an expressible “genetic suicide” gene encoding a heterologousendonuclease, wherein the chromosome of the minicell-producing bacteriacomprises one or more recognition sites of the endonuclease; a definedauxotrophy; and a deletion or mutation in the lpxM/msbB gene.

In some embodiments, the endonuclease is selected from I-CeuI, PI-SceI,I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI,I-DmoI, I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In some embodiments, theauxotrophy is due to a deletion or inactivating mutation in an essentialmetabolic gene. In some embodiments, the expressible gene encoding theminicell-producing gene product is selected from ftsZ, sulA, ccdB, andsfiC.

In some embodiments, the cholesterol-dependent cytolysin protein isselected from listeriolysin O, listeriolysin O L461T, listeriolysin OE247M, listeriolysin O D320K, listeriolysin O E247M, listeriolysin OD320K, listeriolysin O L461T, streptolysin O, streptolysin O c,streptolysin O e, sphaericolysin, anthrolysin O, cereolysin,thuringiensilysin O, weihenstephanensilysin, alveolysin, brevilysin,butyriculysin, tetanolysin O, novyilysin, lectinolysin, pneumolysin,mitilysin, pseudopneumolysin, suilysin, intermedilysin, ivanolysin,seeligeriolysin O, vaginolysin, and pyolysin. In some embodiments, thecholesterol-dependent cytolysin protein is perfringolysin O. In someembodiments, the cholesterol-dependent cytolysin protein comprises SEQID NO: 1.

In some embodiments, the minicell further comprises a recombinantexpression cassette capable of the functional expression of invasin.

Some embodiments provide a method of treating cancer, comprisingadministering to a patient in need thereof a bacterial minicellcomprising a cholesterol-dependent cytolysin protein, wherein saidadministration induces a non-immunogenic anti-tumor immunomodulatoryeffect.

In some embodiments, the minicell does not display an antibody or othermolecule comprising an Fc region of an antibody.

In some embodiments, the cholesterol-dependent cytolysin protein isselected from listeriolysin O, listeriolysin O L461T, listeriolysin OE247M, listeriolysin O D320K, listeriolysin O E247M, listeriolysin OD320K, listeriolysin O L461T, streptolysin O, streptolysin O c,streptolysin O e, sphaericolysin, anthrolysin O, cereolysin,thuringiensilysin O, weihenstephanensilysin, alveolysin, brevilysin,butyriculysin, tetanolysin O, novyilysin, lectinolysin, pneumolysin,mitilysin, pseudopneumolysin, suilysin, intermedilysin, ivanolysin,seeligeriolysin O, vaginolysin, and pyolysin. In some embodiments, thecholesterol-dependent cytolysin protein is perfringolysin O. In someembodiments, the cholesterol-dependent cytolysin protein comprises SEQID NO: 1.

In some embodiments, the minicell further comprises invasin. In someembodiments, the minicell does not comprise invasin.

In some embodiments, the minicell further comprises a Th1 cytokine. Insome embodiments, the Th1 cytokine is selected from IL-2, GMCSF,IL-12p40, IL-12p70, IL-18, TNF-α, and IFN-γ.

In some embodiments, the minicell further comprises a Th2 cytokine. Insome embodiments, the Th2 cytokine is selected from IL-1α, IL-1β, IL-4,IL-5, IL-6, IL-10, and IL-13.

In some embodiments, the minicell further comprises a phospholipase. Insome embodiments, the phospholipase is PC-PLC or PI-PLC.

In some embodiments, the method further comprises a protein toxinselected from fragments A/B of diphtheria toxin, fragment A ofdiphtheria toxin, anthrax toxins LF and EF, adenylate cyclase toxin,gelonin, botulinolysin B, botulinolysin E3, botulinolysin C, botulinumtoxin, cholera toxin, clostridium toxins A, B and alpha, ricin, shiga Atoxin, shiga-like A toxin, cholera A toxin, pertussis S1 toxin,Pseudomonas exotoxin A, E. coli heat labile toxin (LTB), melittin,activated caspases, pro-caspases, cytokines, chemokines,cell-penetrating peptides, and combinations thereof.

In some embodiments, the minicell does not comprise any othertherapeutically-active moiety. In some embodiments, the minicell doesnot comprise a therapeutic small molecule, any other therapeuticprotein, or a therapeutic nucleic acid. In some embodiments, theminicell does not display the Fc binding portion of Protein G or ProteinA.

In some embodiments, the cancer comprises a solid tumor, metastatictumor, or liquid tumor. In some embodiments, the cancer is ofepithelial, fibroblast, muscle or bone origin. In some embodiments, thecancer is selected from breast, lung, pancreatic, prostatic, testicular,ovarian, gastric, intestinal, mouth, tongue, pharynx, hepatic, anal,rectal, colonic, esophageal, gall bladder, skin, uterine, vaginal,penal, and renal cancers. In some embodiments, the cancer is urinarybladder cancer. In some embodiments, the cancer is selected fromadenocarcinomas, sarcomas, fibrosarcomas, and cancers of the eye, brain,and bone. In some embodiments, the cancer is selected from non-Hodgkin'slymphoma, myeloma, Hodgkin's lymphoma, acute lymphocytic leukemia,chronic lymphocytic leukemia, acute myeloid leukemia, and chronicmyeloid leukemia.

In some embodiments, the administration generates a Th1-dominated immuneresponse. In some embodiments, the administration generates aTh2-dominated immune response

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a histogram showing the results of a lactate dehydrogenase(LDH) release assay indicates PFO-mediated mammalian cell membranepermeabilization.

FIG. 2 is a plot showing in vitro cytotoxicity of purified recombinantperfringolysin O (BTX-100) versus equivalent amounts of perfringolysin O(PFO) delivered by minicells.

FIG. 3 is a plot showing removal of the targeting moiety invasin had noeffect on anti-tumor activity of minicells containing PFO.

FIG. 4 depicts photographs and a chart showing similar anti-tumoreffects of VAX-IPD minicells in lung and ovarian metastases.

FIG. 5 is a histogram showing VAX-IPD minicells are detectable in thelungs but not the ovaries of mice following intravenous administration.

FIG. 6 is a histogram showing VAX-IPD minicells have little anti-tumoreffect in severely immune compromised NIH-III mice.

FIG. 7 is a plot showing VAX-IP minicells are highly effective in theMB49 murine model of established non-muscle invasive bladder cancer.

FIG. 8 is a schematic illustration for a general scheme of constructionof VAX-IP minicell-producing strains and VAX-IP minicells therefrom.

FIG. 9 is a plasmid map of pVX-336.

FIG. 10 is a plasmid map of pVX-128.

FIG. 11 shows scanning electron micrographs of inducible minicellformation.

FIG. 12 depicts photographs and a chart demonstrating expression ofInvasin and perfringolysin O in VAX-IP minicells.

DETAILED DESCRIPTION Definitions

As used herein, the term “Th1 immunomodulatory minicells” refers tominicells that are capable of stimulating a Th1 immune response.

As used herein, the term “Th2 immunomodulatory minicells” refers tominicells that are capable of stimulating a Th2 immune response.

As used herein, the term “Th1/Th2 immunomodulatory minicells” refers tominicells that are capable of stimulating both a Th1 and Th2 immuneresponse.

As used herein, the term “recombinant invasive immunomodulatoryminicell” refers to a minicell that has been genetically engineered toexpress and display heterologous minicell surface proteins capable ofstimulating internalization into eukaryotic cells.

As used herein, the term “naturally invasive immunomodulatory minicell”refers to a minicell produced from a normally invasive bacterium suchthat said minicells express and display naturally occurring minicellsurface proteins capable of stimulating internalization into eukaryoticcells.

As used herein, the term “immunogenic” refers to an antigen-specifichumoral or cellular immune response, mediated by adaptive immunemechanisms. An immunogenic minicell directs the immune response torespond to a particular and specific antigen and is useful in thecontext of using immunogenic minicells as a vaccine specific for apathogen, for example.

As used herein, the term “immunomodulatory” refers to the genericmodulation (i.e. not immunogenic per se) of the immune response in adesired fashion including but not limited the production of Th1 and Th2immune responses.

As used herein, the term “immunotherapy” refers to the use of animmunomodulatory compound, for example an immunomodulatory minicell, togenerate a generic (i.e. not immunogenic per se) immune response thathas beneficial effect with respect to the elimination or slowing theprogression of disease, especially cancer.

As used herein, the term “adherent minicell” refers to a minicell thatis capable of binding and adhering to the surface of anon-constitutively phagocytic eukaryotic cell without stimulatingappreciable endocytosis of said minicells.

As used herein, the term “muco-adherent minicell” refers to a minicellthat is capable of binding and adhering to a mucosal surface.

As used herein, the term “VAX-P minicells” refers to minicells thatexpress and comprise perfringolysin O (PFO).

As used herein, the term “VAX-IP minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells further compriseperfringolysin O (PFO).

As used herein, the term “VAX-IPT minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells further compriseperfringolysin O (PFO) and a protein toxin.

As used herein, the term “VAX-IPP minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells comprise perfringolysin O(PFO) and an exogenous polypeptide other than a protein toxin.

As used herein, the term “VAX-IPD minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells comprise perfringolysin O(PFO) and the catalytic fragment of diphtheria toxin.

As used herein, the term “VAX-IPG minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells comprise perfringolysin O(PFO) and gelonin.

As used herein, the term “VAX-IPPA minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells comprise perfringolysin O(PFO) and Pseudomonas exotoxin A.

As used herein, the term “VAX-IPR minicells” refers to minicells thatexpress and display the pan-Beta1-integrin-targeting cell surfacemolecule Invasin from Yersinia pseudotuberculosis and any functionalequivalents thereof, wherein the minicells comprise perfringolysin O(PFO) and ricin A.

As used herein, the term “pore-forming cytolysin protein” and the term“cholesterol-dependent cytolysin protein” are used interchangeably andrefer to a protein that can attack cell membranes that comprisecholesterol to form pore(s) on the cell membrane. For somecholesterol-dependent cytolysin proteins, the presence of cholesterol inthe cell membrane is not required for the cholesterol-dependentcytolysin protein to bind to the cell membrane. For example, thecholesterol-dependent cytolysin protein can be a member of the family ofβ-barrel pore-forming exotoxins secreted by Gram-positive bacteria.Non-limiting examples of cholesterol-dependent cytolysin proteinsinclude listeriolysin O, listeriolysin O L461T, listeriolysin O E247M,listeriolysin O D320K, listeriolysin O E247M, listeriolysin O D320K,listeriolysin O L461T, streptolysin O, streptolysin O c, streptolysin Oe, sphaericolysin, anthrolysin O, cereolysin, thuringiensilysin O,weihenstephanensilysin, alveolysin, brevilysin, butyriculysin,tetanolysin O, novyilysin, lectinolysin, pneumolysin, mitilysin,pseudopneumolysin, suilysin, intermedilysin, ivanolysin, seeligeriolysinO, vaginolysin, pyolysin, and perfringolysin O. In some embodiments, thecholesterol-dependent cytolysin protein comprises an amino acid sequenceof ECTGLAWEWWR (SEQ ID NO: 1). In some embodiments, thecholesterol-dependent cytolysin protein comprises an amino acid sequenceof WEWWRT (SEQ ID NO: 2).

As used herein, the term “therapeutic nucleic acid” refers to a nucleicacid molecule that has a therapeutic effect when introduced into aeukaryotic organism (e.g., a mammal such as human). A therapeuticnucleic acid can be, for example, a ssDNA, a dsDNA, a ssRNA (including ashRNA), a dsRNA (including siRNA), a tRNA (including a rare codon usagetRNA), a mRNA, a micro RNA (miRNA), a ribosomal RNA (rRNA), a peptidenucleic acid (PNA), a DNA:RNA hybrid, an antisense oligonucleotide, aribozyme, an aptamer, or any combination thereof.

As used herein, the term “therapeutic protein” refers to a protein thathas a therapeutic effect when introduced into a eukaryotic organism(e.g., a mammal such as human). A therapeutic polypeptide can be, forexample, a protein toxin, a cholesterol-dependent cytolysin, afunctional enzyme, an activated caspase, a pro-caspase, a cytokine, achemokine, a cell-penetrating peptide, or any combination and/orplurality of the proceeding.

As used herein, the term “therapeutic” means having a biological effector combination of biological effects that prevents, inhibits,eliminates, or prevents progression of a disease or other aberrantbiological processes in an animal. A therapeutically-active moiety caninclude, for example, a therapeutically active small molecule, atherapeutically active protein, and/or a therapeutically active nucleicacid,

As used herein, the term “small molecule” refers to a molecule that hasa biological effect and that has a molecular weight of less than 5000Daltons. In some embodiments, small molecules have a molecular weight ofless than 2500 Daltons. In some embodiments, small molecules have amolecular weight of less than 1000 Daltons. In some embodiments, smallmolecules have a molecular weight of less than 800 Daltons. In someembodiments, small molecules have a molecular weight of less than 500Daltons.

As used herein, the term “therapeutic small molecule drug” or “smallmolecule drug” refers to a small molecule that has a therapeutic effectwhen introduced into a eukaryotic organism (e.g., a mammal such ashuman).

As used herein, the term “beta1 integrin invasin target” refers to amammalian beta1 integrin heterodimer capable of being bound by invasin.

As used herein, the term “prokaryotic cell division gene” refers to agene that encodes a gene product that participates in the prokaryoticcell division process. Many cell division genes have been discovered andcharacterized in the art. Examples of cell division genes include, butare not limited to, zipA, sulA, secA, dicA, dicB, dicC, dicF, ftsA,ftsI, ftsN, ftsK, ftsL, ftsQ, ftsW, ftsZ, minC, minD, minE, seqA, ccdB,sfiC, and ddlB.

As used herein, the term “transgene” refers to a gene or geneticmaterial that has been transferred naturally or by any of a number ofgenetic engineering techniques from one organism to another. In someembodiments, the transgene is a segment of DNA containing a genesequence that has been isolated from one organism and is introduced intoa different organism. This non-native segment of DNA may retain theability to produce RNA or protein in the transgenic organism, or it mayalter the normal function of the transgenic organism's genetic code. Insome embodiments, the transgene is an artificially constructed DNAsequence, regardless of whether it contains a gene coding sequence,which is introduced into an organism in which the transgene waspreviously not found.

As used herein, an agent is said to have been “purified” if itsconcentration is increased, and/or the concentration of one or moreundesirable contaminants is decreased, in a composition relative to thecomposition from which the agent has been purified. In some embodiments,purification includes enrichment of an agent in a composition and/orisolation of an agent therefrom.

The term “sufficiently devoid of parental cells”, synonymous with“sufficiently devoid”, as used herein refers to a composition ofpurified minicells that have a parental cell contamination level thathas little or no effect on the toxicity profile and/or therapeuticeffect of targeted therapeutic minicells.

The term “domain” or “protein domain” used herein refers to a region ofa molecule or structure that shares common physical and/or chemicalfeatures. Non-limiting examples of protein domains include hydrophobictransmembrane or peripheral membrane binding regions, globular enzymaticor receptor regions, protein-protein interaction domains, and/or nucleicacid binding domains.

The terms “Eubacteria” and “prokaryote” are used herein as these termsare used by those in the art. The terms “eubacterial” and “prokaryotic”used herein encompass Eubacteria, including both Gram-negative andGram-positive bacteria, prokaryotic viruses (e.g., bacteriophage), andobligate intracellular parasites (e.g., Richettsia, Chlamydia, etc.).

The term “immunopotentiating polypeptide” is synonomous with“immunostimulatory polypeptide’ and “immunomodulatory polypeptide” andthe terms are used interchangeably herein to refer to any collection ofdiverse protein molecule types that have an immunomodulatory effect whenintroduced into a eukaryotic organism or cell (e.g., a mammal such ashuman). An immunomodulatory polypeptide can be a cytokine, a chemokine,a cholesterol-dependent cytolysin, a functional enzyme, an antibody orantibody mimetic, an activated caspase, a pro-caspase, a cytokine, achemokine, a cell-penetrating peptide, or any combination and/orplurality of the proceeding.

The terms “immunogen” and “antigen” are interchangeable and used hereinto refer to polypeptides, carbohydrates, lipids, nucleic acids, andother molecules to which an antigen-specific antibody, cellular, and/orallergenic response may be mounted against. In the context of thepresent invention, “immunogenicity”, synonomous with “antigenicity” ofthe minicell is not responsible for the immunotherapeutic effect.Antigen-specific immune responses rely on the presence of theantigen/immunogen, and are not be included in the definition of Th1 orTh2 immunomodulatory responses as used herein.

The term “overexpression” used herein refers to the expression of afunctional nucleic acid, polypeptide or protein encoded by DNA in a hostcell, wherein the nucleic acid, polypeptide or protein is either notnormally present in the host cell, or wherein the nucleic acid,polypeptide or protein is present in the host cell at a higher levelthan that normally expressed from the endogenous gene encoding thenucleic acid, polypeptide or protein.

The term “modulate” as used herein means to interact with a targeteither directly or indirectly so as to alter the activity of the targetto regulate a biological process. The mode of “modulate” includes, butis not limited to, enhancing the activity of the target, inhibiting theactivity of the target, limiting the activity of the target, andextending the activity of the target.

The term “heterologous” as used herein refers to a protein, gene,nucleic acid, imaging agent, buffer component, or any other biologicallyactive or inactive material that is not naturally found in a minicell orminicell-producing bacterial strain that is expressed, transcribed,translated, amplified or otherwise generated by minicell-producingbacterial strains that harbor recombinant genetic material coding forsaid heterologous material or coding for genes that are capable ofproducing said heterologous material (e.g., a bioactive metabolite notnative to the parent cell).

The term “exogenous” as used herein refers to a protein (includingantibodies), gene, nucleic acid, small molecule drug, imaging agent,buffer, radionuclide, or any other biologically active or inactivematerial that is not native to a cell, or in the case of a minicell, notnative to the parent cell of the minicell. Exogenous material differsfrom heterologous material by virtue of the fact that it is generated,purified, and added separately.

The term “therapeutic” as used herein means having a biological effector combination of biological effects that prevents, inhibits,eliminates, or prevents progression of a disease or other aberrantbiological processes in an animal.

The term “diagnostic” as used herein means having the ability to detect,monitor, follow, and/or identify a disease or condition in an animal(including humans) or from a biological sample including but not limitedto blood, urine, saliva, sweat and fecal matters.

The term “theranostic” as used herein means having the combined effectsof a therapeutic and a diagnostic composition.

The term “recombinantly expressed” as used herein means the expressionof one or more nucleic acid(s) and/or protein(s) from a nucleic acidmolecule that is constructed using modern genetic engineering techniqueswherein the constructed nucleic acid molecule does not occur naturallyin minicells and/or minicell-producing bacterial strains wherein theartificial nucleic acid molecule is present as an episomal nucleic acidmolecule or as part of the minicell-producing bacterial chromosome.

The term “episomal” as used herein means a nucleic acid molecule that isindependent of the chromosome(s) of a given organism or cell.

The term “detoxified” as used herein refers to a modification made to acomposition or component thereof that results in a significant reductionin acute toxicity to the modified composition or component thereof,regardless of what the causative biological basis for toxicity to thecomposition or component thereof happens to be.

As used herein, the term “bioactive molecule” refers to a moleculehaving a biological effect on a eukaryotic organism or cell (e.g., amammal such as human) when introduced into the human organism or cell.Bioactive molecules include, but are not limited to, therapeutic nucleicacids, therapeutic polypeptides (including protein toxins), andtherapeutic small molecule drugs.

Description

The present application relates to the use of bacterial minicells invitro and in vivo to stimulate the immune system in such a way as tohave an indirect anticancer effect mediated by said immune response.Eubacterial minicells have distinct advantage as immunomodulators, inthat they mimic live bacteria but are not alive and are not infectiousand therefore have reduced toxicity when compared to live bacterialimmunomodulatory therapies. In addition, bacterial minicells may begenetically engineered such that contain different molecularconstituents, each of which may preferentially enhance, invoke, orotherwise incite a certain type of immune response (i.e. Th1 versusTh2). Bacterial minicells disclosed herein are designed to generateimmune responses that have indirect anticancer activity in addition toany direct anti-tumor activity. The minicells may also specificallytarget cell types or tissues known to be involved in the initiation,promotion, support, and maintenance of an immunological response in ananimal. The present application provides use of bacterial minicells asnon-living immunomodulatory therapies for cancer and other diseases.

Bacterial minicells are achromosomal, membrane-encapsulated biologicalnanoparticles (approximately 250-500 nm in diameter) that are formed bybacteria following a disruption in the normal division apparatus ofbacterial cells. In essence, minicells are small, metabolically activereplicas of normal bacterial cells with the exception that they containno chromosomal DNA and as such, are non-dividing, non-viable, andnon-infectious. Although minicells do not contain bacterial chromosomes,plasmid DNA molecules (smaller than chromosomes), RNA molecules (of allsubtypes and structures), native and/or recombinantly expressedproteins, and other metabolites have all been shown to segregate intominicells. Minicells are uniquely suited as in vivo immunomodulatorsbecause they can be engineered to combine one or more differentnaturally occurring, heterologous, or exogenous immunomodulatorymolecular components into a single particle where each component ispresent in discreet amounts. This is in stark contrast to live bacterialbased immunotherapies where live bacteria are capable of continuing todivide, persist, and generate unknown quantities of immunomodulatorycomponents de novo after administration in vivo. Persistence andpropagation of living bacterial immunotherapies can lead to manydifferent complications including infection, organ failure, sepsis, anddeath. In short, minicells can be “engineered” to preferentiallyencapsulate, be coupled to, or absorb biologically active molecules,including various nucleic acids, proteins, small molecule drugs, and anycombination thereof for subsequent generation of immunomodulatoryresponses in both prophylactic and therapeutic medicinal applicationswhere the prevention, maintenance, and/or inhibition of disease by wayof said immunomodulatory response is desirable.

Genetically engineered bacterial minicells have been used directly asanti-cancer agents as described in U.S. Pat. No. 7,183,105, which isincorporated herein by reference in its entirety. For example, it hasbeen taught within U.S. Pat. No. 7,183,105 that minicells can beengineered to use minicell surface-localized antibodies to target anddeliver small molecule drugs, peptides, proteins, and various nucleicacids, together or in concert directly to cancer cells to exert a directtargeted anticancer effect. Other investigators have also reported thesame findings as those taught in U.S. Pat. No. 7,183,105, with respectto the use of minicells as targeted delivery vehicles, as illustrated inU.S. Patent Publication Nos. 20070298056, 20080051469, and 20070237744,each of which is incorporated herein by reference. None of thesereferences teach that minicells can be engineered and utilized asanti-cancer immunotherapies, capable of exerting indirect anti-tumoreffects. Rather, each reference teaches the same approach of usingminicells to specifically target and deliver anti-cancer agents onlydirectly to tumor cells in vivo. The references included abovecollectively teach away from the use of bacterial minicells to causenon-immunogenic immunomodulatory effects when used as cancertherapeutics in vivo. For example, U.S. Pat. No. 7,183,105 describesseveral approaches that may be taken to lessen or evade immune responsesincluding the use of minicells from L-form bacteria (containing no outermembrane) as well generating protoplasts (contain no outer membrane andno cell wall). Examples provided in U.S. Patent Publication Nos.20070298056, 20080051469, and 20070237744 indicate that targeting, usingan antibody selective for a known tumor selective cell surface receptorcoupled to the surface of the minicell vehicle is required foranti-tumor activity. Further, these references also indicate that whennon-targeted minicells are used, that no significant anti-tumor responseis observed. In other related work, MacDiarmid and colleaguesdemonstrate that both non-targeted minicells and tumor-targetedminicells containing no cytotoxic drug payload, are equally incapable ofgenerating an anti-tumor response and that both a targeting antibody andthe cytotoxic payload are required (MacDiarmid, et al. Cancer Cell,2007, Volume 11, p. 431-445). Additionally, MacDiarmid et al. discussthe benefits of evading the immune system, describe such evasion as partof their rationale for design, and therefore explicitly teach away fromusing minicells as immunomodulatory therapeutics. In contrast, thepresent disclosure provides, for example, the use of bacterial minicellsas immunomodulatory therapeutics capable of eliciting potent, indirect,anti-tumor activity. For example, the minicells disclosed herein can beused to induce a non-immunogenic anti-tumor immunomodulatory effect in asubject.

In some embodiments, the present disclosure provides the use ofbacterial minicells as immunomodulatory therapeutics capable ofeliciting potent anti-tumor effects by simultaneous direct and indirectmechanisms mediated by direct tumor targeting and concomitant anti-tumorimmunomodulatory effects, respectively. For example, the minicells canbe designed to stimulate, non-specifically, an anti-cancer immuneresponse while also working specifically, and in concert with saidimmune response, by also delivering a toxic payload directly to cancercells. Thus, some embodiments of the present disclosure relates todirect killing of tumor cells and/or tumor endothelial cells by targeteddrug delivery using minicells and by the indirect non-specific adjuvanteffect involving activation of NK and other immune cell activitiesincluding but not limited to the release of cytokines typical of a Th1response.

As disclosed herein, other live bacterial therapies have been employedas anti-cancer agents in the past but have been limited by toxicity dueto their viable nature. The purveyors of these technologies claim thatliving bacterial therapies work by preferentially colonizing the hypoxicregions of tumors, invading tumor cells in the process, and causingfurther necrosis. Importantly, each of these technologies stresses theimportance of having a live bacterial formulation to achieve efficacyand some go so far as to demonstrate the inactivity of killed bacterialtherapies. These examples would not lead a skilled practitioner toutilize minicells, yet, rather to avoid doing so by teaching thatbacterial viability, colonization of, and persistence within tumortissue is paramount to efficacy. Minicells are not viable, do notpersist and therefore, would not be expected to have an effect, giventhe teachings of those utilizing live bacterial therapies. In contrastto these teachings, the present disclosure makes use of self-limiting,non-living minicells, incapable of persisting in vivo, as animmunotherapy against cancer.

The immunomodulatory therapy disclosed herein may be used with any tumortype. One of ordinary skill in the art will appreciate that certaintumor types may be more susceptible and therefore potentially moreamenable to this approach to therapy. For example, immunomodulatorytherapy and minicells disclosed herein can be used to treat invasivebladder cancer. Over 300,000 new cases of bladder cancer are reportedworldwide every year, 70% of which are detected early at the non-muscleinvasive stage. This population is typically broken down into threestages of disease termed Ta, T1, and T is whereby the tumor is papillary(formerly referred to as superficial), has invaded the lamnia propriabut not yet the muscle, and carcinoma in situ (flat non-invasive tumor),respectively. Each tumor type is then further broken down by grading(grades 1-3) based on different factors including proliferative indexand the like. The standard of care for low risk disease, based on stageand grading, is transuretheral resection of bladder tumor (TURBT)followed by immediate post-operative administration of achemotherapeutic agent. The recommended standard of care forintermediate risk patients is TURBT, followed by immediate postoperativeinstallation of chemotherapy, followed by a 6 week induction treatmentwith chemotherapy. In the event the patient fails chemotherapy, a secondcystoscopic resection is performed and the patient given a liveattenuated strain of Mycobacterium bovis, Bacille Calmette-Guerin (BCG),14 days later. The chemotherapeutic of choice for immediatepostoperative installation is mytomycin C, although doxorubicin,epirubicin, valrubicin, paclitaxel, and gemcitabine have all beenutilized with similar effect. In high risk disease, including thosepatients presenting with carcinoma in situ, BCG is the only effectiveagent. BCG immunomodulatory treatment is far superior to that of any ofthe chemotherapeutics employed to date in the intermediate and high riskpopulation but it is limited in that it cannot be administered immediatepostoperatively. The risk associated with systemic absorption of liveBCG should the bladder be perforated during the TURBT procedure is toogreat to justify its use in the immediate postoperative setting, eventhough BCG-mediated immunomodulation is a far superior approach tochemotherapy with respect to observed recurrence rates. Therefore, mosturologists tend to wait the 14 days to administer BCG, while foregoingthe recommended immediate postoperative installation. On the other hand,outcomes, also in terms of recurrence, are much better if treatment isinitiated using the immediate postoperative clinical treatmentguidelines. Taken together, there is a clear need for a non-livingimmunomodulatory therapy that can be administered immediatelypostoperatively, unlike BCG, to patients having received TURBT fornon-muscle invasive bladder cancer. Moreover, an estimated 30% ofpatients who receive BCG voluntarily halt therapy because of the toxicside effects. Toxicity has been demonstrated to be a function of BCGviability. Therefore, great need exists for a therapeutic agent that canimpart the same immunomodulatory benefit of BCG, but without the risk ofinfection or the viability-associated toxicities.

In some embodiments, immunomodulatory minicells can be utilized as anintravesically administered immunotherapy in (i) the immediatepostoperative setting in non-muscle invasive bladder cancer, (ii) inlieu of BCG therapy for induction and maintenance therapies of the sameand (iii) as a salvage therapy for BCG-intolerant and BCG-refractorypatients. In no way is this method of use meant to limit the presentdisclosure but rather to exemplify the need for effective, non-living,immunotherapies for use in cancer. In addition, the use of multi-effectintegrin-targeted immunomodulatory minicells, which contain the integrintargeting moiety invasin on the minicell surface in conjunction with oneor more combinations of encapsulated cytotoxic polypeptides, endosomaldisrupting polypeptides, small molecule drugs, or nucleic acids, are ofbenefit in bladder cancer because they are capable of causing bothdirect tumor cell killing effects and tumor endothelial cell killingeffects by way of integrin targeting and delivery, while still exertingadditional indirect anti-tumor immunomodulatory effects commissioned bythe immune system. One non-limiting application of multi-effectintegrin-targeted cytotoxic immunomodulatory minicells in bladdercancer, is the use of VAX-IP, which is the minicell comprisingsurface-localized integrin targeting moiety invasin, and perfringolysinO. VAX-IP can be used as an immunomodulatory therapy and/or as a directanti-tumor/tumor endothelial cell therapy. Another non-limitingapplication of multi-effect integrin-targeted cytotoxic immunomodulatoryminicells in bladder cancer, is the use of VAX-IPD, which is theminicell comprising surface-localized integrin targeting moiety invasin,the catalytic fragment of diphtheria toxin, and perfringolysin O.VAX-IPD can be used as an immunomodulatory therapy and/or as a directanti-tumor/tumor endothelial cell therapy.

In some embodiments, minicells are engineered and utilized to generateTh1-dominated immune responses. The Th1 immunomodulatory minicells arecapable of generating the production of Th1 cytokines and chemokinesincluding but not limited to IFN-γ, IFN-α, IL-12, IL-2, GMCSF, IL-18,TGF-β, and TNF-α.

The minicell disclosed herein, in some embodiments, comprises acholesterol-dependent cytolysin protein. In some embodiments, theminicell does not display a molecule comprising an Fc region of anantibody. The molecule comprising an Fc region of an antibody can, forexample, be an antibody or an antibody derivative. In some embodiments,the minicell does not comprise invasin. In some embodiments, theminicell does not comprise a therapeutic small molecule and/or atherapeutic nucleic acid. In some embodiments, the minicell also doesnot comprise any therapeutic protein other than a protein toxin, a Th1cytokin, a Th2 cytokine, a phospholipase, and/or a cholesterol-dependentcytolysin protein. In some embodiments, the minicell does not compriseany therapeutically-active moiety other than a protein toxin, a Th1cytokin, a Th2 cytokine, a phospholipase, and/or a cholesterol-dependentcytolysin protein. In some embodiments, the amount ofcholesterol-dependent cytolysin protein on the minicell is at a leveltoxic to a mammalian cell when the minicell contacts said mammaliancell.

In some embodiments, Th1 immunomodulatory minicells include but are notlimited to those produced from naturally invasive strains of bacteria,including but not limited, to invasive strains of Salmonella spp.,Listeria spp., Mycobacterium spp., Shigella spp., Yersinia spp., andEscherichia coli. These naturally invasive Th1 immunomodulatoryminicells will display naturally occurring minicell surface-localizedligands that are capable of stimulating internalization of minicellsinto eukaryotic cells, to aid in generating Th1-dominantimmunotherapeutic responses. One of ordinary skill in the art willappreciate that naturally-invasive minicells do not exist in nature perse but rather are engineered from non-minicell producing invasivestrains of bacteria using one or more of the genetic approaches togenerating minicells as described herein.

In some embodiments, naturally invasive Th1 immunomodulatory minicellsfurther comprise one or more recombinantly expressed proteins andnucleic acids designed to further enhance, modulate, or stabilizeTh1-dominant immune responses. The recombinantly expressed proteinsinclude, but are not limited to, Th1 cytokines such as IL-2, GMCSF,IL-12p40, IL-12p70, IL-18, TNF-α, and IFN-γ. In addition, naturallyinvasive Th1 immunomodulatory minicells may express one or morepore-forming cytolysin proteins, such as such as listeriolysin O (LLO)and any functional variants or equivalents thereof to facilitateendosomal escape of minicell constituents into the cytosol of cells thathave internalized said minicells to enhance, modulate, or stabilizeTh1-dominant immune responses mediated by said minicells.Phospholipases, such as PC-PLC or PI-PLC, can also be used as endosomaldisrupting agents utilized to enhance, modulate, or stabilizeTh1-dominant immune responses by enhancing minicell constituent releasefrom the endosome into the cytosol of eukaryotic cells that haveinternalized said minicells. Naturally invasive Th1 immunomodulatoryminicells can express a combination of one or more of a Th1 cytokine andone or more endosomal disrupting cytolysins. Naturally invasive Th1immunomodulatory minicells may also contain recombinantly expressedprotein toxins to promote necrosis and/or apoptosis which in turn canalso further enhance, modulate, and/or stabilize Th1 immune responses.The preferred recombinantly expressed/produced protein toxin isperfringolysin O. Other recombinantly expressed/produced protein toxinsto be utilized using naturally invasive Th1 immunomodulatory minicellsinclude but are not limited to fragments A/B of diphtheria toxin,fragment A of diphtheria toxin, anthrax toxins LF and EF, adenylatecyclase toxin, gelonin, botulinolysin B, botulinolysin E3, botulinolysinC, botulinum toxin, cholera toxin, clostridium toxins A, B and alpha,ricin, shiga A toxin, shiga-like A toxin, cholera A toxin, pertussis S1toxin, Pseudomonas exotoxin A, E. coli heat labile toxin (LTB),melittin, pH stable variants of listeriolysin O (pH-independent; aminoacid substitution L461T), thermostable variants of listeriolysin O(amino acid substitutions E247M, D320K), pH and thermostable variants oflisteriolysin O (amino acid substitutions E247M, D320K, and L461T),streptolysin O, streptolysin O c, streptolysin O e, sphaericolysin,anthrolysin O, cereolysin, thuringiensilysin O, weihenstephanensilysin,alveolysin, brevilysin, butyriculysin, tetanolysin O, novyilysin,lectinolysin, pneumolysin, mitilysin, pseudopneumolysin, suilysin,intermedilysin, ivanolysin, seeligeriolysin O, vaginolysin, andpyolysin, activated caspases, pro-caspases, cytokines, chemokines,cell-penetrating peptides, and any combination of the precedingexamples. Recombinant expression of polypeptides(s) can be the result ofexpression from any of the various episomal recombinant prokaryoticexpression vectors known in the art including but not limited toplasmids, cosmids, phagemids, and bacterial artificial chromosomes(BACs), and any combination of the preceding examples. In similarfashion, recombinant expression can be achieved by a chromosomallylocated prokaryotic expression cassette present in one or more copies ofthe minicell-producing parent cell chromosome. Naturally invasive Th1immunomodulatory minicells can also be engineered to express or containone or more immunomodulatory nucleic acids known to stimulateendosome-localized Toll-like receptors 3, 7, 8, and/or 9 to enhance Th1immunomodulatory effects. Such nucleic acids include but are not limitedto single stranded DNA, single stranded RNA, double stranded DNA, doublestranded RNA, DNA hairpins, and RNA hairpins, each of which can berecombinantly expressed as will be readily recognized by those skilledin the art. In some embodiments, naturally invasive Th1 immunomodulatoryminicells are derived from a minicell-producing strain that harbors thehoming endonuclease genetic suicide system of U.S. Patent PublicationNo. 20100112670, incorporated herein by reference. The I-ceuI homingendonuclease described therein selectively digests the chromosomes ofmost bacterial species at discreet conserved sites, serving on one handto selectively kill parental cells and on the other to generate doublestranded DNA fragments in the process.

Some embodiments provide a naturally invasive Th1 immunomodulatoryminicell-producing bacterium comprising: (i) an expressible geneencoding a minicell-producing gene product that modulates one or more ofseptum formation, binary fission, and chromosome segregation; and (ii) aprotein toxin capable of stimulating an immunotherapeutic effect,including but not limited to perfringolysin O. In some embodiments, thebacterium does not display an antibody or other molecule comprising anFc region of an antibody and does not display the Fc binding portion ofProtein G or Protein A. In some embodiments, the naturally invasive Th1immunomodulatory minicell-producing bacterium further comprises one ormore of (iii) an expressible “genetic suicide” gene encoding aheterologous endonuclease, where the chromosome of the naturallyinvasive Th1 immunomodulatory minicell-producing bacteria comprises oneor more recognition sites of the endonuclease; (iv) a definedauxotrophy; and (v) a deletion or mutation in the lpxM/msbB gene (orother functional equivalent). In some embodiments, theminicell-producing gene is a cell division gene. Examples of the celldivision gene include, but are not limited to ftsZ, sulA, ccdB, andsfiC. In some embodiments, the minicell-producing gene is expressedunder the control of an inducible promoter. In some embodiments, theendonuclease suicide gene is located on the chromosome of theminicell-producing bacteria. In some embodiments, the endonuclease is ahoming endonuclease. The homing endonuclease includes, but is notlimited to, I-CeuI, PI-SceI, I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI,I-SceII, I-SceIV, I-CsmI, I-DmoI, I-PorI, PI-TliI, PI-TliII, andPI-ScpI. In some embodiments, the endonuclease is expressed under thecontrol of an inducible promoter. In some embodiments, the auxotrophy isdue to a deletion or inactivating mutation in an essential metabolicgene. In some embodiments, the deletion or inactivating mutation is inthe dapA gene or its functional homolog. In some embodiments, theminicell-producing bacteria further comprises a deletion or aninactivating mutation in a gene encoding a gene product that is involvedin lipopolysaccharide synthesis, wherein the gene is geneticallymodified compared to a corresponding wild-type gene. In someembodiments, the inactivated gene is lpxM/msbB which encodes a geneproduct that causes the bacteria to produce an altered lipid A moleculecompared to lipid A molecules in a corresponding wild-type bacterium. Insome embodiments, the altered lipid A molecule is deficient with respectto the addition of myristolic acid to the lipid A portion of thelipopolysaccharide molecule compared to lipid A molecules in acorresponding wild-type bacterium. In some embodiments, theminicell-producing bacteria further comprise a deletion or inactivatingmutation in a gene that is involved in homologous recombination, wherethe gene is genetically modified compared to a corresponding wild-typegene, where the minicell-producing bacteria are deficient in DNA damagerepair, reducing the risk of recovery from the genetic suicidemechanism. In some embodiments the naturally invasive Th1immunomodulatory minicell-producing bacterium is a Gram-negativebacterium including but not limited to invasive strains of Yersiniaspp., Campylobacter spp., Pseudomonas spp., Salmonella spp., Shigellaspp., Rickettsia spp., and Escherichia coli. In some embodiments, thenaturally invasive Th1 immunomodulatory minicell-producing bacterium isa Gram-positive bacterium including but not limited to Mycobacteriumspp., Streptococcus spp., Listeria monocytogenes, Chlamydia spp., andBrucella spp.

Th1 immunomodulatory minicells include but are not limited to thoseproduced from non-invasive strains of bacteria that have beengenetically engineered to become invasive. Many non-invasive strains ofbacteria are known to the skilled artisan and include but are notlimited to non-invasive strains of Escherichia coli, Salmonella spp.,Shigella spp., Lactobacillus spp., Pseudomonas spp., and the like. Thesenormally non-invasive strains are genetically modified to displayheterologous minicell surface-localized ligands capable of stimulatinginternalization of minicells into eukaryotic cells. The resultingrecombinant invasive Th1 immunomodulatory minicells can be internalizedby immune and other eukaryotic cells to generate Th1-dominantimmunotherapeutic responses. In some embodiments, recombinant invasiveTh1 immunomodulatory minicells further comprise one or morerecombinantly expressed immunomodulatory proteins and nucleic acidsdesigned to further enhance, modulate, or stabilize Th1-dominant immuneresponses. Examples of the immunomodulatory protein include but are notlimited to Th1 cytokines such as IL-2, GMCSF, IL-12p40, IL-12p70, IL-18,TNF-α, and IFN-γ. Recombinant invasive Th1 immunomodulatory minicellsmay express one or more pore-forming cytolysin proteins, such aslisteriolysin O (LLO) and any functional variants or equivalents thereofto facilitate endosomal escape of minicell constituents into the cytosolof cells that have internalized the minicells to enhance, modulate, orstabilize Th1-dominant immune responses mediated by the minicells.Phospholipases, such as PC-PLC or PI-PLC, can also be used as endosomaldisrupting agents utilized to enhance, modulate, or stabilizeTh1-dominant immune responses by enhancing minicell constituent releasefrom the endosome into the cytosol of eukaryotic cells that haveinternalized the minicells. Recombinant invasive Th1 immunomodulatoryminicells can express a combination of one or more of a Th1 cytokine andone or more endosomal disrupting cytolysins. Naturally invasive Th1immunomodulatory minicells can also contain recombinantly expressedprotein toxins to promote necrosis and/or apoptosis which in turn canalso further enhance, modulate, and/or stabilize Th1 immune responses.The preferred recombinantly expressed/produced protein toxin isperfringolysin O. Other examples of recombinantly expressed/producedprotein toxins that can be utilized using recombinant invasive Th1immunomodulatory minicells include but are not limited to fragments A/Bof diphtheria toxin, fragment A of diphtheria toxin, anthrax toxins LFand EF, adenylate cyclase toxin, gelonin, botulinolysin B, botulinolysinE3, botulinolysin C, botulinum toxin, cholera toxin, clostridium toxinsA, B and alpha, ricin, shiga A toxin, shiga-like A toxin, cholera Atoxin, pertussis S1 toxin, Pseudomonas exotoxin A, E. coli heat labiletoxin (LTB), melittin, pH stable variants of listeriolysin O(pH-independent; amino acid substitution L461T), thermostable variantsof listeriolysin O (amino acid substitutions E247M, D320K), pH andthermostable variants of listeriolysin O (amino acid substitutionsE247M, D320K, and L461T), streptolysin O, streptolysin O c, streptolysinO e, sphaericolysin, anthrolysin O, cereolysin, thuringiensilysin O,weihenstephanensilysin, alveolysin, brevilysin, butyriculysin,tetanolysin O, novyilysin, lectinolysin, pneumolysin, mitilysin,pseudopneumolysin, suilysin, intermedilysin, ivanolysin, seeligeriolysinO, vaginolysin, and pyolysin, activated caspases, pro-caspases,cytokines, chemokines, cell-penetrating peptides, and any combination ofthe preceding examples. Recombinant expression of polypeptides(s) can bethe result of expression from any of the various episomal recombinantprokaryotic expression vectors known in the art including but notlimited to plasmids, cosmids, phagemids, and bacterial artificialchromosomes (BACs), and any combination of the preceding examples. Insimilar fashion, recombinant expression can be achieved by achromosomally located prokaryotic expression cassette present in one ormore copies of the minicell-producing parent cell chromosome.Recombinant invasive Th1 immunomodulatory minicells can also beengineered to express or contain one or more immunomodulatory nucleicacids known to stimulate endosome-localized Toll-like receptors 3, 7, 8,and/or 9 to enhance Th1 immunomodulatory effects. Such nucleic acidsinclude but are not limited to single stranded DNA, single stranded RNA,double stranded DNA, linear double stranded DNA, double stranded RNA,DNA hairpins, and RNA hairpins, each of which can be recombinantlyexpressed as will be readily recognized by those skilled in the art. Insome embodiments, recombinant invasive Th1 immunomodulatory minicellsare derived from a minicell-producing strain that harbors the homingendonuclease genetic suicide system of U.S. Patent Publication No.2010-0112670, which is incorporated herein by reference. The I-CeuIhoming endonuclease described therein selectively digests thechromosomes of most bacterial species at discreet, conserved sites,serving on one hand to selectively kill parental cells, and on theother, to generate double stranded linear DNA fragments in the process.

Some embodiments provide a recombinant invasive Th1 immunomodulatoryminicell-producing bacterium comprising: (i) an expressible geneencoding a minicell-producing gene product that modulates one or more ofseptum formation, binary fission, and chromosome segregation; (ii) arecombinant expression cassette capable of the functional expression andsurface display of one or more heterologous minicell surface-localizedtargeting moieties capable of stimulating internalization intoeukaryotic cells, and (iii) a protein toxin capable of stimulating animmunotherapeutic effect, including but not limited to perfringolysin O.The recombinant invasive Th1 immunomodulatory minicell-producingbacterium can also include, in some embodiments, one or more of (iv) anexpressible “genetic suicide” gene encoding a heterologous endonuclease,where the chromosome of the minicell-producing bacteria comprises one ormore recognition sites of the endonuclease; (v) a defined auxotrophy;and (vi) a deletion or mutation in the lpxM/msbB gene (or otherfunctional equivalent). In some embodiments, the minicell-producing geneis a cell division gene. The cell division gene includes, but is notlimited to ftsZ, sulA, ccdB, and sfiC. In some embodiments, theminicell-producing gene is expressed under the control of an induciblepromoter. In some embodiments, the endonuclease suicide gene is locatedon the chromosome of the minicell-producing bacteria. In someembodiments, the endonuclease is a homing endonuclease. The homingendonuclease includes, but is not limited to, I-CeuI, PI-SceI, I-ChuI,I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI, I-DmoI,I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In some embodiments, theendonuclease is expressed under the control of an inducible promoter. Insome embodiments, the auxotrophy is due to a deletion or inactivatingmutation in an essential metabolic gene. In some embodiments, thedeletion or inactivating mutation is in the dapA gene or its functionalhomolog. In some embodiments, the minicell-producing bacteria furthercomprises a deletion or an inactivating mutation in a gene encoding agene product that is involved in lipopolysaccharide synthesis, whereinthe gene is genetically modified compared to a corresponding wild-typegene. In some embodiments, the inactivated gene is lpxM/msbB whichencodes a gene product that causes the bacteria to produce an alteredlipid A molecule compared to lipid A molecules in a correspondingwild-type bacterium. In some embodiments, the altered lipid A moleculeis deficient with respect to the addition of myristolic acid to thelipid A portion of the lipopolysaccharide molecule compared to lipid Amolecules in a corresponding wild-type bacterium. In some embodiments,the minicell-producing bacteria further comprise a deletion orinactivating mutation in a gene that is involved in homologousrecombination, where the gene is genetically modified compared to acorresponding wild-type gene, where the minicell-producing bacteria aredeficient in DNA damage repair. In some embodiments, the recombinantinvasive Th1 immunomodulatory minicell-producing bacterium is aGram-negative bacterium including but not limited to Campylobacterjejuni, Haemophilus influenzae, Bordetella pertussis, Brucella spp.,Franciscella tularemia, Legionella pneumophilia, Neisseria meningitidis,Kliebsella, Yersinia spp., Helicobacter pylori, Neisseria gonorrhoeae,Legionella pneumophila, Salmonella spp., Shigella spp., Pseudomonasspp., and Escherichia coli. In some embodiments, the recombinantinvasive Th1 immunomodulatory minicell-producing bacterium is aGram-positive bacterium including but not limited to Staphylococcusspp., Lactobacillus spp., Streptococcus spp., Bacillus subtilis,Clostridium difficile, and Bacillus cereus.

In some embodiments, Th1 immunomodulatory minicells are produced fromnon-invasive strains of bacteria. Many non-invasive strains of bacteriaare known to the skilled artisan and include but are not limited tonon-invasive strains of Escherichia coli, Salmonella spp., Shigellaspp., Lactobacillus spp., Pseudomonas spp., and the like. Thesenon-invasive Th1 immunomodulatory minicells can be internalized byimmune and other eukaryotic cells to generate Th1-dominantimmunotherapeutic responses. In some embodiments, recombinantnon-invasive Th1 immunomodulatory minicells further comprise one or morerecombinantly expressed immunomodulatory proteins and nucleic acidsdesigned to further enhance, modulate, or stabilize Th1-dominant immuneresponses. Examples of the immunomodulatory protein include but are notlimited to Th1 cytokines such as IL-2, GMCSF, IL-12p40, IL-12p70, IL-18,TNF-α, and IFN-γ. Recombinant non-invasive Th1 immunomodulatoryminicells may express one or more pore forming cytolysin proteins, suchas such as listeriolysin O (LLO) and any functional variants orequivalents thereof to facilitate endosomal escape of minicellconstituents into the cytosol of cells that have internalized saidminicells to enhance, modulate, or stabilize Th1-dominant immuneresponses mediated by said minicells. Phospholipases, such as PC-PLC orPI-PLC, can also be used as endosomal disrupting agents utilized toenhance, modulate, or stabilize Th1-dominant immune responses byenhancing minicell constituent release from the endosome into thecytosol of eukaryotic cells that have internalized said minicells.Recombinant non-invasive Th1 immunomodulatory minicells can express acombination of one or more of a Th1 cytokine and one or more endosomaldisrupting cytolysins. Recombinant non-invasive Th1 immunomodulatoryminicells can also contain recombinantly expressed protein toxins topromote necrosis and/or apoptosis which in turn can also furtherenhance, modulate, and/or stabilize Th1 immune responses. The preferredrecombinantly expressed/produced protein toxin is perfringolysin O.Other recombinantly expressed/produced protein toxins to be utilizedusing recombinant non-invasive Th1 immunomodulatory minicells includebut are not limited to fragments A/B of diphtheria toxin, fragment A ofdiphtheria toxin, anthrax toxins LF and EF, adenylate cyclase toxin,gelonin, botulinolysin B, botulinolysin E3, botulinolysin C, botulinumtoxin, cholera toxin, clostridium toxins A, B and alpha, ricin, shiga Atoxin, shiga-like A toxin, cholera A toxin, pertussis S1 toxin,Pseudomonas exotoxin A, E. coli heat labile toxin (LTB), melittin, pHstable variants of listeriolysin O (pH-independent; amino acidsubstitution L461T), thermostable variants of listeriolysin O (aminoacid substitutions E247M, D320K), pH and thermostable variants oflisteriolysin O (amino acid substitutions E247M, D320K, and L461T),streptolysin O, streptolysin O c, streptolysin O e, sphaericolysin,anthrolysin O, cereolysin, thuringiensilysin O, weihenstephanensilysin,alveolysin, brevilysin, butyriculysin, tetanolysin O, novyilysin,lectinolysin, pneumolysin, mitilysin, pseudopneumolysin, suilysin,intermedilysin, ivanolysin, seeligeriolysin O, vaginolysin, andpyolysin, activated caspases, pro-caspases, cytokines, chemokines,cell-penetrating peptides, and any combination of the precedingexamples. Recombinant expression of polypeptides(s) can be the result ofexpression from any of the various episomal recombinant prokaryoticexpression vectors known in the art including but not limited toplasmids, cosmids, phagemids, and bacterial artificial chromosomes(BACs), and any combination of the preceding examples. In similarfashion, recombinant expression can be achieved by a chromosomallylocated prokaryotic expression cassette present in one or more copies ofthe minicell-producing parent cell chromosome. Recombinant non-invasiveTh1 immunomodulatory minicells can also be engineered to express orcontain one or more immunomodulatory nucleic acids known to stimulateendosome-localized Toll-like receptors 3, 7, 8, and/or 9 to enhance Th1immunomodulatory effects. Such nucleic acids include but are not limitedto single stranded DNA, single stranded RNA, double stranded DNA, lineardouble stranded DNA, double stranded RNA, DNA hairpins, and RNAhairpins, each of which can be recombinantly expressed as will bereadily recognized by those skilled in the art. In some embodiments,recombinant non-invasive Th1 immunomodulatory minicells are derived froma minicell-producing strain that harbors the homing endonuclease geneticsuicide system described in U.S. Patent Publication No. 2010-0112670,incorporated herein by way of reference. The I-CeuI homing endonucleasedescribed therein selectively digests the chromosomes of most bacterialspecies at discreet, conserved sites, serving on one hand to selectivelykill parental cells, and on the other, to generate double strandedlinear DNA fragments in the process.

Some embodiments provide a recombinant non-invasive Th1 immunomodulatoryminicell-producing bacterium comprising: (i) an expressible geneencoding a minicell-producing gene product that modulates one or more ofseptum formation, binary fission, and chromosome segregation; and (ii) aprotein toxin capable of stimulating an immunotherapeutic effect,including but not limited to perfringolysin O. In some embodiments, therecombinant non-invasive Th1 immunomodulatory minicell-producingbacterium further comprises one or more of (iii) an expressible “geneticsuicide” gene encoding a heterologous endonuclease, where the chromosomeof the recombinant non-invasive Th1 immunomodulatory minicell-producingbacteria comprises one or more recognition sites of the endonuclease;(iv) a defined auxotrophy; and and (v) a deletion or mutation in thelpxM/msbB gene (or other functional equivalent). In some embodiments,the minicell-producing gene is a cell division gene. The cell divisiongene includes, but is not limited to ftsZ, sulA, ccdB, and sfiC. In someembodiments, the minicell-producing gene is expressed under the controlof an inducible promoter. In some embodiments, the endonuclease suicidegene is located on the chromosome of the minicell-producing bacteria. Insome embodiments, the endonuclease is a homing endonuclease. Examples ofthe homing endonuclease include, but are not limited to, I-CeuI,PI-SceI, I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV,I-CsmI, I-DmoI, I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In someembodiments, the endonuclease is expressed under the control of aninducible promoter. In some embodiments, the auxotrophy is due to adeletion or inactivating mutation in an essential metabolic gene. Insome embodiments the deletion or inactivating mutation is in the dapAgene or its functional homolog. In some embodiments, theminicell-producing bacteria further comprises a deletion or aninactivating mutation in a gene encoding a gene product that is involvedin lipopolysaccharide synthesis, wherein the gene is geneticallymodified compared to a corresponding wild-type gene. In someembodiments, the inactivated gene is lpxM/msbB which encodes a geneproduct that causes the bacteria to produce an altered lipid A moleculecompared to lipid A molecules in a corresponding wild-type bacterium. Insome embodiments, the altered lipid A molecule is deficient with respectto the addition of myristolic acid to the lipid A portion of thelipopolysaccharide molecule compared to lipid A molecules in acorresponding wild-type bacterium. In some embodiments, theminicell-producing bacteria further comprise a deletion or inactivatingmutation in a gene that is involved in homologous recombination, wherethe gene is genetically modified compared to a corresponding wild-typegene, where the minicell-producing bacteria are deficient in DNA damagerepair, reducing the risk of recovery from the genetic suicidemechanism. In some embodiments, the recombinant non-invasive Th1immunomodulatory minicell-producing bacterium is a Gram-negativebacterium including but not limited to invasive strains of Yersiniaspp., Campylobacter spp., Pseudomonas spp., Salmonella spp., Shigellaspp., Rickettsia spp., and Escherichia coli. In some embodiments therecombinant non-invasive Th1 immunomodulatory minicell-producingbacterium is a Gram-positive bacterium including but not limited toMycobacterium spp., Streptococcus spp., Listeria monocytogenes,Chlamydia spp., and Brucella spp.

In some embodiments, minicells are engineered and utilized to generateTh2-dominated immune responses. Examples of the Th2 immunomodulatoryminicell capable of generating the production of Th2 cytokines andchemokines include, but are not limited to, IL-1α, IL-1β, IL-4, IL-5,IL-6, IL-10, and IL-13.

In some embodiments, Th2 immunomodulatory minicells include but are notlimited to those produced from naturally occurring non-invasive,adherent, or muco-adhesive strains of bacteria including but not limitedto non-invasive, adherent, and muco-adhesive strains of Streptococcusspp., Staphylococcus spp., Salmonella spp., Shigella spp., Lactobacillusspp., Pseudomonas spp., Klebsiella spp., and Escherichia coli. Thesenaturally non-invasive Th2 immunomodulatory minicells do not displaynaturally occurring minicell surface-localized ligands that are capableof stimulating internalization of minicells into eukaryotic cells,though they may be engulfed by constitutively phagocytic immune cellssuch as macrophages, dendritic cells, and neutrophils. Adherent andmuco-adherent Th2 immunomodulatory minicells express minicell surfacelocalized proteins that can stimulate adherence to the surfaces ofeukaryotic cells and mucosal surfaces, respectively, yet do not causeappreciable internalization, the exception being for normallyconstitutively phagocytic cells such as macrophages, neutrophils, anddendritic cells. One of ordinary skill in the art will appreciate thatnaturally-noninvasive Th2 immunomodulatory minicells, adherent Th2immunomodulatory minicells, and muco-adherent Th2 immunomodulatoryminicells do not exist in nature per se but rather are engineered fromnon-minicell producing non-invasive, adherent, and muco-adherent speciesof bacteria using one or more of the genetic approaches to generatingminicells as described herein. Non-adherent strains of Streptococcusspp., Staphylococcus spp., Salmonella spp., Shigella spp., Lactobacillusspp., Pseudomonas spp., Klebsiella spp., and Escherichia coli are easilyengineered by those skilled in the art of molecular biology and/ormicrobial genetics to become adherent by cloning and recombinantexpression of bacterial cell surface adherence factors such thatexpression of said heterologous adherence factors results in recombinantadherent Th2 immunomodulatory minicells.

Some embodiments provide a naturally non-invasive, adherent, ormuco-adherent Th2 immunomodulatory minicell-producing bacteriumcomprising: (i) an expressible gene encoding a minicell-producing geneproduct that modulates one or more of septum formation, binary fission,and chromosome segregation. In some embodiments, the naturallynon-invasive, adherent, or muco-adherent Th2 immunomodulatoryminicell-producing bacterium further comprises one or more of (ii) anexpressible “genetic suicide” gene encoding a heterologous endonuclease,where the chromosome of the naturally non-invasive, adherent, and/ormuco-adherent Th2 immunomodulatory minicell-producing bacteria comprisesone or more recognition sites of the endonuclease; (iii) a definedauxotrophy; and (iv) a deletion or mutation in the lpxM/msbB gene (orother functional equivalent. In some embodiments, the minicell-producinggene is a cell division gene. The cell division gene includes, but isnot limited to ftsZ, sulA, ccdB, and sfiC. In some embodiments, theminicell-producing gene is expressed under the control of an induciblepromoter. In some embodiments, the endonuclease suicide gene is locatedon the chromosome of the minicell-producing bacteria. In someembodiments, the endonuclease is a homing endonuclease. Examples of thehoming endonuclease include, but are not limited to, I-CeuI, PI-SceI,I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI,I-DmoI, I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In some embodiments, theendonuclease is expressed under the control of an inducible promoter. Insome embodiments, the auxotrophy is due to a deletion or inactivatingmutation in an essential metabolic gene. In some embodiments, thedeletion or inactivating mutation is in the dapA gene or its functionalhomolog. In some embodiments, the minicell-producing bacteria furthercomprises a deletion or an inactivating mutation in a gene encoding agene product that is involved in lipopolysaccharide synthesis, whereinthe gene is genetically modified compared to a corresponding wild-typegene. In some embodiments, the inactivated gene is lpxM/msbB whichencodes a gene product that causes the bacteria to produce an alteredlipid A molecule compared to lipid A molecules in a correspondingwild-type bacterium. In some embodiments, the altered lipid A moleculeis deficient with respect to the addition of myristolic acid to thelipid A portion of the lipopolysaccharide molecule compared to lipid Amolecules in a corresponding wild-type bacterium. In some embodiments,the minicell-producing bacteria further comprise a deletion orinactivating mutation in a gene that is involved in homologousrecombination, where the gene is genetically modified compared to acorresponding wild-type gene, where the minicell-producing bacteria aredeficient in DNA damage repair, reducing the risk of recovery from thegenetic suicide mechanism. In some embodiments the naturallynon-invasive, adherent, and/or muco-adherent Th2 immunomodulatoryminicell-producing bacterium is a Gram-negative bacterium including butnot limited to invasive strains of Yersinia spp., Campylobacter spp.,Pseudomonas spp., Salmonella spp., Shigella spp., Rickettsia spp., andEscherichia coli. In some embodiments, the naturally non-invasive,adherent, or muco-adherent Th2 immunomodulatory minicell-producingbacterium is a Gram-positive bacterium including but not limited toMycobacterium spp., Streptococcus spp., Listeria monocytogenes,Chlamydia spp., and Brucella spp.

Some embodiments provide multi-effect targeted cytotoxicimmunomodulatory minicells. Multi-effect targeted cytotoxicimmunomodulatory minicells contain a minicell surface localizedtargeting moiety, a cytotoxic payload, and/or endosomal escape protein.Multi-effect targeted cytotoxic immunomodulatory minicells are capableof eliciting direct anti-tumor effects by way of targeting anddelivering a cytotoxic payload directly to tumor cells in addition tobeing able to evoke a Th1 immunomodulatory effect that results infurther anti-tumor activity.

As described herein, VAX-IP minicells encompass all multi-effectcytotoxic immunomodulatory minicells that express and display invasinand perfringolysin O in concert. It is preferred that the finalpreparation of minicells is comprised of detoxified LPS and issufficiently devoid of any in vivo viable contaminating parent cells byvirtue of the novel, inducible genetic suicide mechanism and DAPauxotrophy.

As described herein, VAX-IPT minicells encompass all multi-effectcytotoxic immunomodulatory minicells that express and display invasin,perfringolysin O, and a protein toxin in concert. It is preferred thatthe final preparation of minicells is comprised of detoxified LPS and issufficiently devoid of any in vivo viable contaminating parent cells byvirtue of the novel, inducible genetic suicide mechanism and DAPauxotrophy.

As described herein, one non-limiting preferred sub-class of VAX-IPTminicell is VAX-IPD minicell, which is a multi-effect cytotoxicimmunomodulatory minicell expressing and displaying invasin,perfringolysin O, and the catalytic fragment (fragment A) of diphtheriatoxin in concert. It is preferred that the final preparation ofminicells is comprised of detoxified LPS and is sufficiently devoid ofany in vivo viable contaminating parent cells by virtue of a novel,inducible genetic suicide mechanism and DAP auxotrophy. In someembodiments, VAX-IPD bacterial minicells are used to target and moreefficiently deliver the catalytic fragment of diphtheria toxin in vitroand in vivo. For example, optimal killing activity is observed in thepresence of all three of invasin, PFO, and the catalytic fragment(fragment A) of diphtheria toxin. And, VAX-IPD has similar requirementsfor all three components in order to exert broad spectrum potency acrossa panel of murine and human endothelial and tumor cell types known toexpress activated beta1 integrins. Surprisingly, HL60 cells which arealso known to express beta1 integrins, are not affected by VAX-IPD. Thisresult is unexpected and upon further review of the literature, it wasdiscovered that HL60 cells express beta1 integrins but in an unactivatedform. However, invasin activity, which has been thoroughlycharacterized, has never been reported to be dependent on beta1activation status per se. This unexpected result is likely alsocontributing to the lack of expected toxicity demonstrated in vivo asbeta1 integrins are expressed in many tissue types, albeit in mostinstances at very low levels, and are also found in ligand bound orunactivated form. Importantly, it is observed that VAX-IPD minicells arecapable of preventing or eliminating metastases as well as exertingprimary anti-tumor effects in vivo. Similar results, with respect toactivity and toxicity, albeit in a different model, are also observed.

Protein G is a cell-surface protein expressed by the Gram-positivebacterium Group G Streptococcus. Its natural biological function is toprevent opsonization of Group G Streptococcus during the infectionprocess by binding the Fc region of antibodies such that the Fc regionis masked from the immune system. Protein G contains two Fc bindingdomains. In some embodiments, the minicells does not have the Fc bindingportion of protein G. In some embodiments, the minicells does notdisplay the Fc binding portion of protein G.

Protein A is a cell-surface protein expressed by the Gram-positivebacterium Staphylococcus aureus. Like Protein G, its natural biologicalfunction is also to prevent opsonization of Staphylococcus aureus duringthe infection process. Staphylococcus aureus use Protein A to bind tothe Fc region of antibodies. Protein A contains four discreet Fc bindingdomains. In some embodiments, the minicells does not have the Fc bindingportion of protein A. In some embodiments, the minicells does notdisplay the Fc binding portion of protein A.

The minicells disclosed herein, in some embodiments, do not comprise anantibody or other molecule comprising an Fc region of an antibody. Theminicells disclosed herein, in some embodiments, do not display anantibody or other molecule comprising an Fc region of an antibody.

Some embodiments provide a VAX-P minicell-producing bacteriumcomprising: (i) an expressible gene encoding a minicell-producing geneproduct that modulates one or more of septum formation, binary fission,and chromosome segregation; and (ii) a recombinant expression cassettecapable of the functional expression of perfringolysin O. In someembodiments, the bacterium does not display an antibody or othermolecule comprising an Fc region of an antibody and does not display theFc binding portion of Protein G or Protein A. In some embodiments, theVAX-P minicell-producing bacterium further comprises one or more of(iii) an expressible “genetic suicide” gene encoding a heterologousendonuclease, where the chromosome of the minicell-producing bacteriacomprises one or more recognition sites of the endonuclease; (iv) adefined auxotrophy; and (v) a deletion or mutation in the lpxM/msbB gene(or other functional equivalent). In some embodiments, theminicell-producing gene is a cell division gene. Examples of the celldivision gene include, but are not limited to ftsZ, sulA, ccdB, andsfiC. In some embodiments, the minicell-producing gene is expressedunder the control of an inducible promoter. In some embodiments, theendonuclease suicide gene is located on the chromosome of theminicell-producing bacteria. In some embodiments, the endonuclease is ahoming endonuclease. Examples of the homing endonuclease include, butare not limited to, I-CeuI, PI-SceI, I-ChuI, I-CpaI, I-SceIII, I-CreI,I-MsoI, I-SceII, I-SceIV, I-CsmI, I-DmoI, I-PorI, PI-TliI, PI-TliII, andPI-ScpI. In some embodiments, the endonuclease is expressed under thecontrol of an inducible promoter. In some embodiments, the auxotrophy isdue to a deletion or inactivating mutation in an essential metabolicgene. In some embodiments, the deletion or inactivating mutation is inthe dapA gene or its functional homolog. In some embodiments, theminicell-producing bacteria further comprises a deletion or aninactivating mutation in a gene encoding a gene product that is involvedin lipopolysaccharide synthesis, wherein the gene is geneticallymodified compared to a corresponding wild-type gene. In someembodiments, the inactivated gene is lpxM/msbB which encodes a geneproduct that causes the bacteria to produce an altered lipid A moleculecompared to lipid A molecules in a corresponding wild-type bacterium. Insome embodiments, the altered lipid A molecule is deficient with respectto the addition of myristolic acid to the lipid A portion of thelipopolysaccharide molecule compared to lipid A molecules in acorresponding wild-type bacterium. In some embodiments, theminicell-producing bacteria further comprise a deletion or inactivatingmutation in a gene that is involved in homologous recombination, wherethe gene is genetically modified compared to a corresponding wild-typegene, where the minicell-producing bacteria are deficient in DNA damagerepair. In some embodiments the VAX-P minicell-producing bacterium is aGram-negative bacterium including but not limited to Campylobacterjejuni, Haemophilus influenzae, Bordetella pertussis, Brucella spp.,Franciscella tularemia, Legionella pneumophilia, Neisseria meningitidis,Kliebsella, Yersinia spp., Helicobacter pylori, Neisseria gonorrhoeae,Legionella pneumophila, Salmonella spp., Shigella spp., Pseudomonasaeruginosa, and Escherichia coli. In some embodiments, the VAX-Pminicell-producing bacterium is a Gram-positive bacterium including butnot limited to Staphylococcus spp., Lactobacillus spp., Streptococcusspp., Bacillus subtilis, Clostridium difficile, and Bacillus cereus.

Some embodiments provide a VAX-IP minicell-producing bacteriumcomprising: (i) an expressible gene encoding a minicell-producing geneproduct that modulates one or more of septum formation, binary fission,and chromosome segregation; and (ii) a recombinant expression cassettecapable of the functional expression and surface display of invasin inaddition to expression of perfringolysin O. In some embodiments, thebacterium does not display an antibody or other molecule comprising anFc region of an antibody and does not display the Fc binding portion ofProtein G or Protein A. In some embodiments, the VAX-IPminicell-producing bacterium further comprises one or more of (iii) anexpressible “genetic suicide” gene encoding a heterologous endonuclease,where the chromosome of the minicell-producing bacteria comprises one ormore recognition sites of the endonuclease; (iv) a defined auxotrophy;and (v) a deletion or mutation in the lpxM/msbB gene (or otherfunctional equivalent). In some embodiments, the minicell-producing geneis a cell division gene. Examples of the cell division gene include, butare not limited to ftsZ, sulA, ccdB, and sfiC. In some embodiments, theminicell-producing gene is expressed under the control of an induciblepromoter. In some embodiments, the endonuclease suicide gene is locatedon the chromosome of the minicell-producing bacteria. In someembodiments, the endonuclease is a homing endonuclease. Examples of thehoming endonuclease include, but are not limited to, I-CeuI, PI-SceI,I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI,I-DmoI, I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In some embodiments, theendonuclease is expressed under the control of an inducible promoter. Insome embodiments, the auxotrophy is due to a deletion or inactivatingmutation in an essential metabolic gene. In some embodiments, thedeletion or inactivating mutation is in the dapA gene or its functionalhomolog. In some embodiments, the minicell-producing bacteria furthercomprises a deletion or an inactivating mutation in a gene encoding agene product that is involved in lipopolysaccharide synthesis, whereinthe gene is genetically modified compared to a corresponding wild-typegene. In some embodiments, the inactivated gene is lpxM/msbB whichencodes a gene product that causes the bacteria to produce an alteredlipid A molecule compared to lipid A molecules in a correspondingwild-type bacterium. In some embodiments, the altered lipid A moleculeis deficient with respect to the addition of myristolic acid to thelipid A portion of the lipopolysaccharide molecule compared to lipid Amolecules in a corresponding wild-type bacterium. In some embodiments,the minicell-producing bacteria further comprise a deletion orinactivating mutation in a gene that is involved in homologousrecombination, where the gene is genetically modified compared to acorresponding wild-type gene, where the minicell-producing bacteria aredeficient in DNA damage repair. In some embodiments the VAX-IPminicell-producing bacterium is a Gram-negative bacterium including butnot limited to Campylobacter jejuni, Haemophilus influenzae, Bordetellapertussis, Brucella spp., Franciscella tularemia, Legionellapneumophilia, Neisseria meningitidis, Kliebsella, Yersinia spp.,Helicobacter pylori, Neisseria gonorrhoeae, Legionella pneumophila,Salmonella spp., Shigella spp., Pseudomonas aeruginosa, and Escherichiacoli. In some embodiments, the VAX-IP minicell-producing bacterium is aGram-positive bacterium including but not limited to Staphylococcusspp., Lactobacillus spp., Streptococcus spp., Bacillus subtilis,Clostridium difficile, and Bacillus cereus.

Some embodiments provide a VAX-IPD minicell-producing bacteriumcomprising: (i) an expressible gene encoding a minicell-producing geneproduct that modulates one or more of septum formation, binary fission,and chromosome segregation; and (ii) a recombinant expression cassettecapable of the functional expression and surface display of invasin inaddition to expression of perfringolysin O and the catalytic fragment(fragment A) of diphtheria toxin. In some embodiments, the bacteriumdoes not display an antibody or other molecule comprising an Fc regionof an antibody and does not display the Fc binding portion of Protein Gor Protein A. In some embodiments, the VAX-IPD minicell-producingbacterium further comprises one or more of (iii) an expressible “geneticsuicide” gene encoding a heterologous endonuclease, where the chromosomeof the minicell-producing bacteria comprises one or more recognitionsites of the endonuclease; (iv) a defined auxotrophy; and (v) a deletionor mutation in the lpxM/msbB gene (or other functional equivalent). Insome embodiments, the minicell-producing gene is a cell division gene.Examples of the cell division gene include, but are not limited to ftsZ,sulA, ccdB, and sfiC. In some embodiments, the minicell-producing geneis expressed under the control of an inducible promoter. In someembodiments, the endonuclease suicide gene is located on the chromosomeof the minicell-producing bacteria. In some embodiments, theendonuclease is a homing endonuclease. Examples of the homingendonuclease include, but are not limited to, I-CeuI, PI-SceI, I-ChuI,I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI, I-DmoI,I-PorI, PI-TliI, PI-TliII, and PI-ScpI. In some embodiments, theendonuclease is expressed under the control of an inducible promoter. Insome embodiments, the auxotrophy is due to a deletion or inactivatingmutation in an essential metabolic gene. In some embodiments, thedeletion or inactivating mutation is in the dapA gene or its functionalhomolog. In some embodiments, the minicell-producing bacteria furthercomprises a deletion or an inactivating mutation in a gene encoding agene product that is involved in lipopolysaccharide synthesis, whereinthe gene is genetically modified compared to a corresponding wild-typegene. In some embodiments, the inactivated gene is lpxM/msbB whichencodes a gene product that causes the bacteria to produce an alteredlipid A molecule compared to lipid A molecules in a correspondingwild-type bacterium. In some embodiments, the altered lipid A moleculeis deficient with respect to the addition of myristolic acid to thelipid A portion of the lipopolysaccharide molecule compared to lipid Amolecules in a corresponding wild-type bacterium. In some embodiments,the minicell-producing bacteria further comprise a deletion orinactivating mutation in a gene that is involved in homologousrecombination, where the gene is genetically modified compared to acorresponding wild-type gene, where the minicell-producing bacteria aredeficient in DNA damage repair. In some embodiments the VAX-IPDminicell-producing bacterium is a Gram-negative bacterium including butnot limited to Campylobacter jejuni, Haemophilus influenzae, Bordetellapertussis, Brucella spp., Franciscella tularemia, Legionellapneumophilia, Neisseria meningitidis, Kliebsella, Yersinia spp.,Helicobacter pylori, Neisseria gonorrhoeae, Legionella pneumophila,Salmonella spp., Shigella spp., Pseudomonas aeruginosa, and Escherichiacoli. In some embodiments, the VAX-IPD minicell-producing bacterium is aGram-positive bacterium including but not limited to Staphylococcusspp., Lactobacillus spp., Streptococcus spp., Bacillus subtilis,Clostridium difficile, and Bacillus cereus.

Minicells have distinct mechanisms and advantages with respect toloading of immunomodulatory polypeptides (e.g. cytokines, proteintoxins, and cytolysins) and nucleic acids (e.g. double stranded RNA,hairpin RNA, double stranded linear DNA). For example, immunomodulatoryminicell-producing parental bacterial cells can be used to recombinantlyexpress/produce one or more cytokines, protein toxins, and cytolysinsprior to or at the same time that minicells are being produced.Recombinant polypeptides are expressed, segregate into, and areencapsulated by minicells, and then utilized to enhance, modulate,and/or stabilize Th1 or Th2 immune responses elicited byimmunomodulatory minicells in vivo. The recombinant production ofvarious immunomodulatory minicell protein components, can include but isnot limited to, perfringolysin O and invasin, can be facilitated by anycombination of recombinant expression methods known to the skilledartisan. By way of non-limiting example, recombinant expression can befacilitated from a chromosomally located operably linked open readingframe coding for a particular protein component, such as invasin.Recombinant expression of protein components of immunomodulatoryminicells can be facilitated by the use of one or more episomalprokaryotic expression constructs such as plasmids, cosmids, phagemids,and bacterial artificial chromosomes (BACs). Operably linked prokaryoticopen reading frames coding for the individual desired protein componentsof the final immunomodulatory minicell product can be present on thesame episomal expression construct or on separate and distinct episomalexpression constructs. The production of the desired protein componentscan be placed under inducible prokaryotic promoter control oralternatively can be placed under the control of a constitutively activeprokaryotic promoter system. One of ordinary skill in the art willreadily recognize the prokaryotic promoter systems available for usewith the present invention. Examples of promoter system include but arenot limited to the IPTG inducible Lac system and its myriad derivatives,the L-rhamnose inducible pRHA system, the L-arabinose inducible pBADsystem, the T7 polymerase system, the CI857ts system, and the like. Onenon-limiting embodiment of generating VAX-IP minicell-producing strainsand VAX-IP minicells there from, is illustrated in Example 6 and FIG. 8.

In cases where polypeptide(s) are pre-formed by the parental cell by wayof recombinant expression from a prokaryotic expression cassette (eitherchromosomal or episomal in location) and then packaged inside of theminicells as an immunopotentiator, the half-life of the polypeptide(s)within the minicell can be increased by use of immunomodulatory minicellproducing bacterial strains harboring one or more deletions or othernon-functional mutations in protease genes (e.g., the lon protease of E.coli) responsible for proteolysis. In the absence of the protease(s),the protein toxin molecules accumulate to a higher level, increasing thepotency of targeted minicells delivering the therapeutic polypeptidemolecules. In the case of Escherichia coli minicell producing strains,mutation or deletions can be introduced into one or more of the lon,tonB, abgA, ampA, ampM, pepP, clpP, dcp, ddpX/vanX, elaD, frvX,gcp/b3064, hslV, hchA/b1967, hyaD, hybD, hycH, hycI, iadA, ldcA, ycbZ,pepD, pepE, pepQ, pepT, pmbA, pqqL, prlG, ptrB, sgcX, sprT, tldD, ycaL,yeaZ, yegQ, ygeY, yggG, yhbO, yibG, ydpF, degS, ftsH/hflB, glpG,hofD/hopD, lepB, lspA, pppA, sohB, spa, yaeL, yfbL, dacA, dacB, dacC,degP/htrA, degQ, iap, mepA, nlpC, pbpG, tsp, ptrA, teas, umuD, ydcP,ydgD, ydhO, yebA, yhbU, yhjJ, and nlpD genes.

In cases where immunomodulatory nucleic acid(s) are pre-formed by theparental cell by way of recombinant expression from a prokaryoticexpression cassette (either chromosomal or episomal in location) andthen packaged inside of the minicells as an immunopotentiator, thehalf-life of the nucleic acid(s) within the minicell is increased by useof immunomodulatory minicell producing bacterial strains harboring oneor more deletions or other non-functional mutations in nuclease genes(e.g., the mc nuclease of E. coli) responsible for double stranded RNAdegradation. In the absence of the nuclease(s), immunomodulatory nucleicacid molecules accumulate to a higher level, increasing the potency ofimmunomodulatory minicells harboring said immunomodulatory nucleic acidmolecules.

In order for immunomodulatory minicells to be used as immunotherapeuticagents in humans, said minicells should contain few or no contaminants,such as viable parental bacterial cells. Levels of viable contaminatingcells and other contaminants must be low enough not to cause adverseside effects in patients or to interfere with minicell activity. Theinducible expression of a homing endonuclease gene, referred to as agenetic suicide mechanism, is a preferred mechanism by which toeliminate live contaminating parental cells, especially when used incombination with conventional filtration methods. Because minicells arederived from some bacteria that are pathogenic or opportunisticallypathogenic, it is desirable that the contaminating parental cells befunctionally eliminated from a given population before systemic, andparticularly intravenous, administration. The same holds true forintravesical administration to non-muscle invasive bladder cancerpatients having received TURBT surgery, especially where a perforationin the bladder has occurred or is suspected. Consequently, the desiredminicell formulation would be one in which the residual live parentalcell count would be as low as possible so as not cause adverse sideeffects or interfere with intended minicell activity. To maximize safetyand limit toxicity due to viability of any contaminating parental cells,the minicells disclosed herein are derived from minicell-producingstrains that comprise safety features, for example, one or more of thethree safety features disclosed below. In some embodiments, theminicell-producing strains comprise at least these three synergisticsafety features. The first is a genetic suicide mechanism that killsresidual live parental cells without lysing them (and expelling freelipopolysaccharide) after the minicell formation step has beencompleted. The present application incorporates the use of a regulatedgenetic suicide mechanism that upon exposure to the appropriate inducer,introduces irreparable damage to the chromosomes of minicell-producingparental cells as described in U.S. Patent Publication No. 20100112670.The suicide mechanism operates to introduce irreparable double-strandedbreaks to the chromosome of the parental cells and can be used as anadjunct to conventional separation techniques to improve minicellpurification. The second safety feature is a defined auxotrophy,preferably but not necessarily in the diaminopimelic acid (DAP)biosynthesis pathway, and most preferably in the dapA gene of an E. coliminicell-producing strain. Minicell-producing strains of E. coli thatexhibit DAP auxotrophy (dapA-) cannot survive outside of the laboratorywithout supplementation of DAP. Further, DAP is not found in mammals,including humans, and as such any minicell-producing parental cell thatis present in the minicell product will not be able to survive in theenvironment or in vivo. Many variations on this theme exist fordifferent Gram-negative and Gram-positive bacteria. For example inSalmonella, spp., auxotrophies in the aromatic amino acid biosynthesispathways (the aro genes) produce in effect, the same result. In the caseof Shigella spp. auxotrophies in the guanine biosynthesis pathway willproduce, in effect, the same result. The third safety feature isoptional and entails a deletion of the lpxM gene in E. coliminicell-producing strains. Deletion of the lpxM gene can result in theproduction of de-toxified lipopolysaccharide (LPS) molecules. The lpxMgene (also referred to as the msbB gene) functions to add a terminalmyristolic acid group to the lipid A portion of the LPS molecule andremoval of this group (by way of elimination of the lpxM gene) resultsin marked detoxification of LPS. Specifically, detoxification ischaracterized by a decrease in the production of pro-inflammatorycytokines in response to exposure to LPS. One of ordinary skill in theart will appreciate that cytokines are still made using the detoxifiedform of LPS. The detoxification controls only the levels of cytokinesproduced, making it possible to dampen the acute sepsis-likepro-inflammatory response while allowing more robust Th1 and/or Th2immune responses, to be achieved without overt toxicity. This deletioncan be introduced into any functionally equivalent gene of anyGram-negative or Gram-positive minicell-producing strain to achieve thesame effect. The enhanced safety profile can reduce the risk ofinfection and potential for developing sepsis, decrease the possibilityof genetic reversion through recombination events with other bacteria,and minimize the risk of insertion events in the host. From a regulatoryand manufacturing perspective, it is also preferred that antibioticresistance markers be eliminated from the bacterial chromosome of theminicell-producing parental cell strain. The use of most antibioticresistance gene markers in minicell-producing strains of bacteria isundesirable in order to comply with regulatory requirements imposed bythe U.S. Food and Drug Administration (FDA) for use in humans. The FDAwill only tolerate the use of the kanamycin resistance gene marker forselection purposes for bacteria or bacterial production strains whereinthe final product is intended for use in humans.

Some embodiments provide a method of making immunomodulatory minicells,comprising culturing the appropriate immunomodulatory minicell-producingbacteria disclosed herein and substantially separating immunomodulatoryminicells from the minicell-producing parent cells, thereby generating acomposition comprising immunotherapeutic minicells. In some embodiments,the method further comprises inducing immunomodulatory minicellformation from a culture of minicell-producing parent cells. In someembodiments, the method further comprises inducing expression of thegene encoding the genetic suicide endonuclease. In some embodiments,minicell formation is induced by the presence of one or more chemicalcompounds selected from isopropyl β-D-1-thiogalactopyranoside (IPTG),rhamnose, arabinose, xylose, fructose, melibiose, and tetracycline. Insome embodiments, the expression of the gene encoding the geneticsuicide endonuclease is induced by a change in temperature. In someembodiments, the method further comprises purifying the immunomodulatoryminicells from the composition. In some embodiments, theimmunomodulatory minicells are substantially separated from the parentcells by a process selected from the group including but not limited tocentrifugation, filtration, ultrafiltration, ultracentrifugation,density gradation, immunoaffinity, immunoprecipitation, and anycombination of the preceding purification methods.

Some embodiments provide a eubacterial minicell comprising an outermembrane, where the lipopolysaccharide constituents of the outermembrane comprises Lipid A molecules having no myristolic acid moiety(“detoxified lipopolysaccharide” or “detoxified LPS”). Detoxified LPSresults in the reduction of pro-inflammatory immune responses in amammalian host compared to the inflammatory response induced by theouter membrane of eubacterial minicells that are derived from acorresponding wild-type bacterium.

The present disclosure describes the novel use of immunomodulatoryeubacterial minicells for purposes of stimulating the immune system insuch a way as to have potent indirect anti-tumor effects mediated, infull or in part, by the immune response in addition to any directanti-tumor effects. For example, the immunomodulatory minicellsdisclosed herein can be used as an intravesical therapy for non-muscleinvasive bladder cancer.

1. Minicell Production

Minicells are achromosomal, membrane-encapsulated biologicalnano-particles (approximately 250-500 nm in diameter depending on thestrain type and growth conditions used) that are formed by bacteriafollowing a disruption in the normal cell division apparatus. Inessence, minicells are small, metabolically active replicas of normalbacterial cells with the exception that they contain no chromosomal DNAand as such, are non-dividing and non-viable. Although minicells do notcontain chromosomal DNA, plasmid DNA, RNA, native and/or recombinantlyexpressed proteins, and other metabolites have all been shown tosegregate into minicells.

Disruptions in the coordination between chromosome replication and celldivision lead to minicell formation from the polar region of mostrod-shaped prokaryotes. Disruption of the coordination betweenchromosome replication and cell division can be facilitated through theover-expression of some of the genes involved in septum formation andbinary fission. Alternatively, minicells can be produced in strains thatharbor mutations in genes involved in septum formation and binaryfission. Impaired chromosome segregation mechanisms can also lead tominicell formation as has been shown in many different prokaryotes.

Similarly, minicell production can be achieved by the over-expression ormutation of genes involved in the segregation of nascent chromosomesinto daughter cells. For example, mutations in the parC or mukB loci ofE. coli have been demonstrated to produce minicells. Both affectseparate requisite steps in the chromosome segregation process inEnterobacteriacea. It can be assumed that like the cell division genesdescribed above, manipulation of wild type levels of any given geneinvolved in the chromosome segregation process that result in minicellproduction will have similar effects in other family members.

Because the cell division and chromosome replication processes are socritical to survival, there exists a high level of genetic andfunctional conservation amongst prokaryotic family members with respectto genes responsible for these processes. As a result, theover-expression or mutation of a cell division gene capable of drivingminicell production in one family member can be used to produceminicells in another. For example, it has been shown that theover-expression of the E. coli ftsZ gene in other Enterobacteriaceafamily members such as Salmonella spp. and Shigella spp as well as otherclass members such as Pseudomonas spp. will result in similar levels ofminicell production.

The same can be demonstrated in the mutation-based minicell producingstrains of the family Enterobacteriacea. For example, deletion of themin locus in any of Enterobacteriacea family members results in minicellproduction. Cell division genes from the Enterobacteriacea in whichmutation can lead to minicell formation include but are not limited tothe min genes (MinCDE). While minicell production from the min mutantstrains is possible, these strains have limited commercial value interms of being production strains. The reason for this is that strainswith deletions or mutations within the min genes make minicells atconstitutively low levels. This presents two problems in terms ofcommercialization and economies of scale. The first is that minicellyields from these strains are low, which increases production cost. Thesecond is that minicell yields are highly variable with the mutantstrains and lot-to-lot variability has an enormous impact on productioncost, manufacturing quality control and regulatory compliance. Usingcell division mutant strains to produce minicells that encapsulatebiologically active molecules such as proteins, RNA, DNA, and othercatabolites for diagnostic or therapeutic delivery is problematic. Theonset of minicell production in the mutant strains cannot be controlledand occurs at a low level so that the end result is that some minicellswill contain no biologically active molecules while others will containwidely variable amounts of biologically active molecules. Theseshortcomings when taken together or separately greatly restrict theutility of these mutant strains for commercial purposes.

Minicell-producing strains that overexpress cell division genes(“overexpressers”) are preferred over mutation-based strains because theminicell-production phenotype is controllable as long as the celldivision genes to be overexpressed are placed under the control of aninducible or other conditionally active eubacterial promoter system.Minicell production from strains overexpressing the cell division geneftsZ were discovered by researchers who were identifying essential celldivision genes in E. coli using plasmid-based complementation studies.In these studies, the ftsZ gene was present in over 10 copies per cell.The presence of multiple gene copies of ftsZ was demonstrated to produceminicells and extremely long filamented cells. Ultimately, thistransition into the irreversible filamentous phenotype negativelyimpacts minicell yields from strains overexpressing ftsZ from multi-copyplasmids, although the number of minicells produced is still higher thanthat of any mutant strain. It has since been demonstrated that byreducing the number of ftsZ gene copies to a single, chromosomalduplication, the number of minicells produced increases over thosestrains where ftsZ is located on multi-copy plasmids and that thefilamentous phenotype is less profound. Thus, the preferredcomposition(s) are minicell-producing strains that inducibly overexpressthe ftsZ gene from a duplicate, chromosomally integrated copy of ftsZ.The duplicate ftsZ gene used can be derived directly from the species ofbacteria in which the minicell-production phenotype is being engineeredand can also be derived from the ftsZ gene sequence from other speciesof bacteria. By way of non-limiting example, overexpression of the ftsZgene of Escherichia coli can be used to generate minicells fromEscherichia coli and Salmonella typhimurium. Resulting strains arecomprised of the wild type ftsZ gene and a separate, duplicative, andinducible copy of the ftsZ gene on the chromosome and the induciblegenetic suicide mechanism(s) described in U.S. patent publication No.2010/0112670, which is incorporated herein by its entirety. By way ofnon-limiting example, division genes that can be over-expressed toproduce minicells in the family Enterobacteriaceae include but are notlimited to ftsZ, minE, sulA, ccdB, and sfiC. The preferred compositionis to have a duplicate copy(s) of a cell division gene(s) under thecontrol of an inducible promoter that is stably integrated into thechromosome of a given eubacterial strain. It is easily recognized by oneskilled in the art that this same strategy could be imparted if theinducible cell division gene cassette were present on a plasmid, cosmid,bacterial artificial chromosome (BAC), recombinant bacteriophage orother episomal DNA molecule present in the cell.

This inducible phenotype approach to minicell production has severaldistinct advantages over the mutant systems. The first is that becausethere are no constitutive genetic mutations in these strains, thereexists no selective pressure during normal growth and the cells of theculture maintain a very stable and normal physiology until the minicellphenotype is induced. The end result is that inducible minicellproducing strains are healthier and more stable, which ultimatelyresults in higher yields of minicells. Another distinct advantage ofusing the inducible phenotype approach to minicell production is incases where minicells are to be used to deliver biologically activemolecules such as proteins, therapeutic RNAs, plasmid DNAs, and otherbioactive catabolites that can be made by the minicell-producing parentcells such that the minicells that are produced encapsulate thosebiologically active molecules. In these cases, the preferred method isto induce the formation of the biologically active molecule(s) withinthe parental cells prior to inducing the minicell phenotype, so that allof the minicells produced will contain the desired amount of thebiologically active molecule(s). Alternatively, the minicells themselvesare capable of producing the bioactive molecule after being separatedfrom the parental cells. This includes but is not limited to forming thebioactive molecule from an episomal nucleic acid or RNA encoding for thebioactive molecule located within the minicell or by preexisting proteinconstituents of minicells after being separated from the parental cells.Any of these expression strategies can be employed to express anddisplay binding moieties on the surfaces of minicells. These advantages,when used in combination, result in a higher quality and quantity ofminicells. In addition, these minicells can further comprise smallmolecule drugs that can be loaded into minicells as described in moredetail below.

2. Minicell Purification

Because minicells are derived from some bacteria that are pathogenic oropportunistically pathogenic, it is of the utmost importance that anycontaminating parental cells be functionally eliminated from a givenpopulation before administration. Conventionally, live parental cellshave been eliminated through either physical means or biological meansor both.

Physical means include the use of centrifugation-based separationprocedures, filtration methodologies, chromatography methodologies, orany combination thereof.

Biological elimination is achieved by but not limited to thepreferential lysis of parental cells, the use of auxotrophic parentalstrains, treatment with antibiotics, treatment with UV radiation,diaminopimelic acid (DAP) deprivation, selective adsorption of parentalcells, treatment with other DNA damaging agents, and induction of asuicide gene.

Preferential lysis of parental cells is typically mediated by inducingthe lytic cycle of a lysogenic prophage. In the case of minicellproducing strains, it is most useful to use a prophage that is lysiscompetent but defective at re-infection, such that minicells are notsubsequently infected and lysed during activation of the lyticphenotype. Alternatively and by way of non-limiting example, individualgenes such as those classified as members of the holin gene family, canbe expressed to achieve similar levels of lysis without the concernsover re-infection inherent to the use of lysogenic prophages. Bothapproaches are limited by the fact that the lysis event, regardless ofthe method used to achieve it, expels unacceptable amounts of freeendotoxin into the media. Removal of such large amounts of freeendotoxin is time consuming, suffers from lot to lot variability, and isultimately cost prohibitive.

The use of auxotrophic strains raises concerns over reversion and assuch can only be used in cases where minicells are to be produced fromcommensal or non-pathogenic strains of bacteria. Thus, their applicationis limited with respect to being used as a method for elimination oflive non-pathogenic parental cells used in minicell production.

Treatment with UV irradiation can be useful in the elimination of liveparental cells on a minicell production run with the exception of thefact that UV irradiation is random with respect to its effects onnucleic acids and results are highly variable from lot to lot. Inaddition, this method is not preferred when using minicells to delivertherapeutic or prophylactic nucleic acids as UV irradiation randomlydamages all nucleic acids. For instance, plasmid DNA would also behighly susceptible to DNA damage by UV irradiation and may be renderedineffective although still effectively delivered by minicells.

Diaminopimelic acid (DAP) deprivation can be useful in the eliminationof live parental cells with the exception that this approach is limitedby the number of species it can be used for. In other words, not allparent cell species capable of producing minicells require DAP forsurvival. DAP mutants in E. coli minicell-producing strains are of greatadvantage and in some cases preferred over the wild type. The advantageof using DAP is that this compound (diaminopimelic acid, an E. coli cellwall constituent) is critical for the growth of E. coli and is notpresent in or produced by animals. Thus, should a “viable” E. coliminicell-producing parental cell be administered along with targetedminicells, the parental cell will be unable to grow and will thereby beinert to the animal and with respect to minicell activity. A similarapproach can be used with Salmonella spp. based minicell-producingparental strains except in that case the aro genes, preferably aroB areremoved.

Selective adsorption methodologies have yet to be explored with respectto purifying minicells from viable parental cells. Selective adsorptionis defined as any process by which parental cells or minicells arepreferentially adsorbed to a substrate by virtue of their affinity forthe substrate. By way of non-limiting example, high affinityprotein-protein interactions could be exploited for this use. By way ofnon-limiting example, the novel minicell outer membrane proteinLpp-OmpA::Protein A has a high affinity for the Fc region of mostantibodies. The gene encoding for Lpp-OmpA::Protein A is under thecontrol an inducible promoter could easily be introduced on to thechromosome of an immunomodulatory minicell producing strain.Immunomodulatory minicells could be produced from this strain prior tothe activation of expression of the invasin gene such that the minicellsproduced do not express or display Lpp-OmpA::Protein A on their cellsurface. Once the desired quantity of immunomodulatory minicells isproduced from the strain, the viable cells within the culture could begiven the signal to produce the Lpp-OmpA::Protein A protein such thatLpp-OmpA::Protein A is only expressed and displayed upon viable cells.Once Lpp-OmpA::Protein A is preferentially expressed on the surface ofviable parental cells, they can be easily adsorbed to a substrate coatedwith antibodies or other Fc-region containing proteins. Once absorbed,minicells can be selectively purified away from viable parental cells bya number of different means dependent upon the substrate type used.Substrates include but are not limited to solid-phase chromatographiccolumns used in gravity filtration applications, magnetic beads, ionexchange columns, or HPLC columns.

In some embodiments, minicells are substantially separated from theminicell-producing parent cells in a composition comprising minicells.For example, after separation, the composition comprising the minicellsis more than about 99.9%, 99.5%, 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%,91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%,77%, 76%, 75%, 74%, 73%, 72%, 71%, 70%, 65%, 60%, 55%, 50%, 45%, 40%,35% or 30% free of minicell-producing parent cells. In some embodiments,the composition contains less than about 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%,6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%,21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30% minicell-producingparent cells.

Preferably, the final composition contains few enough contaminatingparental cells, viable or otherwise, so as not to be too toxic orinterfere with the activity of targeted minicells when administered invivo for therapeutic purposes.

A preferred method of sufficiently eliminating contaminating viableparental bacterial cells or preventing their survival in vivo is throughthe incorporation of an inducible genetic suicide mechanism, includingbut not limited to the activation and expression of a homingendonuclease or functional equivalent thereof as described in U.S.Patent Publication No. 20100112670.

3. Targeting Minicells to Specific Cells, Tissues, and Organs

Following production and subsequent purification, VAX-IP, VAX-IPT,VAX-IPP, VAX-IPD, VAX-IPG, VAX-IPPA, and VAX-IPR minicells can be usedas targeted delivery vehicles to target specific cell types that haveelevated expression and/or activity of beta1-integrins and are involvedin disease in vivo to preferentially and more efficiently deliver theirprotein toxin payloads to the targeted tissue, organ, and cell type. Thetargeted VAX-IP, VAX-IPT, VAX-IPP, VAX-IPD, VAX-IPG, VAX-IPPA, andVAX-IPR minicells disclosed herein can be targeted to eukaryotic cancercell-specific surface antigens that include but are not limited tointegrin α3β1, integrin α4β1, integrin α5β1, integrin α6β1, integrinα_(v)β1, and integrin β1. As described in more detail below, expressionand/or activity levels of these beta1 integrin family members are foundin many solid tumor types as well as in the tumor vasculature ascompared to low level, unactivated, and/or ligand occupied beta1integrins in normal tissues and vasculature.

4. Loading Payloads into Minicells

Eubacterial minicells are capable of encapsulating and deliveringseveral classes of biologically active compounds that have therapeutic,prophylactic, or diagnostic benefit to an animal. Types of thebiologically active compounds (payloads) that can be delivered byminicells include but are not limited to small molecules (includingsmall molecule drugs), nucleic acids, polypeptides, radioisotope,lipids, lipopolysaccharides, and any combination thereof.

Proteins are comprised of polypeptides and are encoded by DNA. Proteinscan be biologically functional, such as enzymes, toxins, or signalingproteins. Proteins can be structural, such as is the case for actin andthe like. Proteins can bind tightly to other proteins, such as withantibodies and antibody mimetics, and be used to disrupt functionsrequiring protein/protein interactions. Proteins can providelocalization signals by being fluorescent or bioluminescent. Proteinscan serve as immunogens or serve other therapeutic purposes (such assupplying or restoring enzyme in a target cell, tissue, organ, oranimal). Proteins can aid in the post-endocytosis intracellular transferof other payload types. For example, proteins such as listeriolysin Ofrom Listeria monocytogenes can be employed to facilitate the transferof the minicell payload(s) from the endocytotic compartment(s) of atarget cell to the cytosol of a target cell. Proteins can also bepro-drug converting enzymes. One non-limiting preferred recombinantlyexpressed/produced protein toxin is perfringolysin O. Otherrecombinantly expressed/produced therapeutic polypeptides to bedelivered by targeted minicells include but are not limited to proteintoxins, cholesterol-dependent cytolysins, functional enzymes, antibodymimetics, protein/protein interaction disrupters, activated caspases,pro-caspases, cytokines, chemokines, cell-penetrating peptides, and anycombination of the proceeding. Recombinant expression of a therapeuticpolypeptide(s) can be the result of expression from any of the variousepisomal recombinant prokaryotic expression vectors known in the artincluding but not limited to plasmids, cosmids, phagemids, and bacterialartificial chromosomes (BACs), and any combination of the preceding. Insimilar fashion, recombinant expression can be achieved by achromosomally located prokaryotic expression cassette present in one ormore copies of the minicell-producing parent cell chromosome. Therecombinant production of various immunomodulatory minicell proteincomponents (including but not limited to perfringolysin O and invasin)can be facilitated by any combination of recombinant expression methodsknown to the skilled artisan. By way of non-limiting example,recombinant expression can be facilitated from a chromosomally locatedoperably linked open reading frame coding for a particular proteincomponent, such as invasin. Recombinant expression of protein componentsof immunomodulatory minicells can be facilitated by the use of one ormore episomal prokaryotic expression constructs such as plasmids,cosmids, phagemids, and bacterial artificial chromosomes (BACs).Operably linked prokaryotic open reading frames coding for theindividual desired protein components of the final immunomodulatoryminicell product can be present on the same episomal expressionconstruct or on separate and distinct episomal expression constructs.The production of the desired protein components can be placed underinducible prokaryotic promoter control or alternatively may be placedunder the control of a constitutively active prokaryotic promotersystem. One of ordinary skill in the art will readily recognize theprokaryotic promoter systems available for use. Examples of promotersystems include but are not limited to the IPTG inducible Lac system andits myriad derivatives, the L-rhamnose inducible pRHA system, theL-arabinose inducible pBAD system, the T7 polymerase system, the CI857tssystem, and the like. By way of non-limiting example, the specificmethods of generating VAX-IP minicell-producing strains and VAX-IPminicells there from, is included as Example 6 and FIG. 8.

Examples of protein toxins include but are not limited to perfringolysinO, gelonin, diphtheria toxin fragment A, diphtheria toxin fragment A/B,tetanus toxin, E. coli heat labile toxin (LTI and/or LTII), choleratoxin, C. perfringes iota toxin, Pseudomonas exotoxin A, shiga toxin,anthrax toxin, MTX (B. sphaericus mosquilicidal toxin), streptolysin,barley toxin, mellitin, anthrax toxins LF and EF, adenylate cyclasetoxin, botulinolysin B, botulinolysin E3, botulinolysin C, botulinumtoxin A, cholera toxin, clostridium toxins A, B, and alpha, ricin, shigaA toxin, shiga-like A toxin, cholera A toxin, pertussis S1 toxin, E.coli heat labile toxin (LTB), pH stable variants of listeriolysin O(pH-independent; amino acid substitution L461T), thermostable variantsof listeriolysin O (amino acid substitutions E247M, D320K), pH andthermostable variants of listeriolysin O (amino acid substitutionsE247M, D320K, and L461T), streptolysin O, streptolysin O c, streptolysinO e, sphaericolysin, anthrolysin O, cereolysin, thuringiensilysin O,weihenstephanensilysin, alveolysin, brevilysin, butyriculysin,tetanolysin O, novyilysin, lectinolysin, pneumolysin, mitilysin,pseudopneumolysin, suilysin, intermedilysin, ivanolysin, seeligeriolysinO, vaginolysin, and pyolysin. Protein toxins may be localized todifferent sub-cellular compartments of the minicell at the discretion ofthe artisan. When targeted minicells disclosed herein are derived from aGram-negative parental minicell-producing strain, recombinantlyexpressed therapeutic polypeptides produced therefrom can be localizedto the cytosol, the inner leaflet of the inner membrane, the outerleaflet of the inner membrane, the periplasm, the inner leaflet of theouter membrane, the outer membrane of minicells, and any combination ofthe proceeding. When targeted minicells disclosed herein are derivedfrom a Gram-positive parental minicell-producing strain, recombinantlyexpressed therapeutic polypeptides produced therefrom can be localizedto the cytosol, the cell wall, the inner leaflet of the membrane, themembrane of minicells, and any combination of the proceeding.

5. Pharmaceutical Compositions

The present application also relates to compositions, including but notlimited to pharmaceutical compositions. The term “composition” usedherein refers to a mixture comprising at least one carrier, preferably aphysiologically acceptable carrier, and one or more minicellcompositions. The term “carrier” used herein refers to a chemicalcompound that does not inhibit or prevent the incorporation of thebiologically active peptide(s) into cells or tissues. A carriertypically is an inert substance that allows an active ingredient to beformulated or compounded into a suitable dosage form (e.g., a pill, acapsule, a gel, a film, a tablet, a microparticle (e.g., a microsphere),a solution; an ointment; a paste, an aerosol, a droplet, a colloid or anemulsion etc.). A “physiologically acceptable carrier” is a carriersuitable for use under physiological conditions that does not abrogate(reduce, inhibit, or prevent) the biological activity and properties ofthe compound. For example, dimethyl sulfoxide (DMSO) is a carrier as itfacilitates the uptake of many organic compounds into the cells ortissues of an organism. Preferably, the carrier is a physiologicallyacceptable carrier, preferably a pharmaceutically or veterinarilyacceptable carrier, in which the minicell composition is disposed.

A “pharmaceutical composition” refers to a composition wherein thecarrier is a pharmaceutically acceptable carrier, while a “veterinarycomposition” is one wherein the carrier is a veterinarily acceptablecarrier. The term “pharmaceutically acceptable carrier” or “veterinarilyacceptable carrier” used herein includes any medium or material that isnot biologically or otherwise undesirable, i.e., the carrier may beadministered to an organism along with a minicell composition withoutcausing any undesirable biological effects or interacting in adeleterious manner with the complex or any of its components or theorganism. Examples of pharmaceutically acceptable reagents are providedin The United States Pharmacopeia, The National Formulary, United StatesPharmacopeial Convention, Inc., Rockville, Md. 1990, hereby incorporatedby reference herein into the present application. The terms“therapeutically effective amount” and “pharmaceutically effectiveamount” refer to an amount sufficient to induce or effectuate ameasurable response in the target cell, tissue, or body of an organism.What constitutes a therapeutically effective amount will depend on avariety of factors, which the knowledgeable practitioner will take intoaccount in arriving at the desired dosage regimen.

The compositions can also comprise other chemical components, such asdiluents and excipients. A “diluent” is a chemical compound diluted in asolvent, preferably an aqueous solvent, that facilitates dissolution ofthe composition in the solvent, and it may also serve to stabilize thebiologically active form of the composition or one or more of itscomponents. Salts dissolved in buffered solutions are utilized asdiluents in the art. For example, preferred diluents are bufferedsolutions containing one or more different salts. An unlimiting exampleof preferred buffered solution is phosphate buffered saline(particularly in conjunction with compositions intended forpharmaceutical administration), as it mimics the salt conditions ofhuman blood. Since buffer salts can control the pH of a solution at lowconcentrations, a buffered diluent rarely modifies the biologicalactivity of a given compound or pharmaceutical composition.

An “excipient” is any more or less inert substance that can be added toa composition in order to confer a suitable property, for example, asuitable consistency or to produce a drug formulation. Suitableexcipients and carriers include, in particular, fillers such as sugars,including lactose, sucrose, mannitol, or sorbitol cellulose preparationssuch as, for example, maize starch, wheat starch, rice starch, agar,pectin, xanthan gum, guar gum, locust bean gum, hyaluronic acid, caseinpotato starch, gelatin, gum tragacanth, methyl cellulose,hydroxypropylmethyl-cellulose, polyacrylate, sodiumcarboxymethylcellulose, and/or polyvinylpyrrolidone (PVP). If desired,disintegrating agents can also be included, such as cross-linkedpolyvinyl pyrrolidone, agar, or alginic acid or a salt thereof such assodium alginate. Other suitable excipients and carriers includehydrogels, gellable hydrocolloids, and chitosan. Chitosan microspheresand microcapsules can be used as carriers. See e.g., WO 98/52547 (whichdescribes microsphere formulations for targeting compounds to thestomach, the formulations comprising an inner core (optionally includinga gelled hydrocolloid) containing one or more active ingredients, amembrane comprised of a water insoluble polymer (e.g., ethylcellulose)to control the release rate of the active ingredient(s), and an outerlayer comprised of a bioadhesive cationic polymer, for example, acationic polysaccharide, a cationic protein, and/or a synthetic cationicpolymer; U.S. Pat. No. 4,895,724. Typically, chitosan is cross-linkedusing a suitable agent, for example, glutaraldehyde, glyoxal,epichlorohydrin, and succinaldehyde. Compositions employing chitosan asa carrier can be formulated into a variety of dosage forms, includingpills, tablets, microparticles, and microspheres, including thoseproviding for controlled release of the active ingredient(s). Othersuitable bioadhesive cationic polymers include acidic gelatin,polygalactosamine, polyamino acids such as polylysine, polyhistidine,polyornithine, polyquaternary compounds, prolamine, polyimine,diethylaminoethyldextran (DEAE), DEAE-imine, DEAE-methacrylate,DEAE-acrylamide, DEAE-dextran, DEAE-cellulose, poly-p-aminostyrene,polyoxethane, copolymethacrylates, polyamidoamines, cationic starches,polyvinylpyridine, and polythiodiethylaminomethylethylene.

The compositions can be formulated in any suitable manner. Minicellcompositions may be uniformly (homogeneously) or non-uniformly(heterogeneously) dispersed in the carrier. Suitable formulationsinclude dry and liquid formulations. Dry formulations include freezedried and lyophilized powders, which are particularly well suited foraerosol delivery to the sinuses or lung, or for long term storagefollowed by reconstitution in a suitable diluent prior toadministration. Other preferred dry formulations include those wherein acomposition disclosed herein is compressed into tablet or pill formsuitable for oral administration or compounded into a sustained releaseformulation. When the composition is intended for oral administration tobe delivered to epithelium in the intestines, it is preferred that theformulation be encapsulated with an enteric coating to protect theformulation and prevent premature release of the minicell compositionsincluded therein. As those in the art will appreciate, the compositionsdisclosed herein can be placed into any suitable dosage form. Pills andtablets represent some of such dosage forms. The compositions can alsobe encapsulated into any suitable capsule or other coating material, forexample, by compression, dipping, pan coating, spray drying, etc.Suitable capsules include those made from gelatin and starch. In turn,such capsules can be coated with one or more additional materials, forexample, and enteric coating, if desired. Liquid formulations includeaqueous formulations, gels, and emulsions.

Some embodiments provide compositions that comprise a bioadhesive,preferably a mucoadhesive, coating. A “bioadhesive coating” is a coatingthat allows a substance (e.g., a minicell composition) to adhere to abiological surface or substance better than occurs absent the coating. A“mucoadhesive coating” is a preferred bioadhesive coating that allows asubstance, for example, a composition to adhere better to mucosa occursabsent the coating. For example, minicells can be coated with amucoadhesive. The coated particles can then be assembled into a dosageform suitable for delivery to an organism. Preferably, and dependingupon the location where the cell surface transport moiety to be targetedis expressed, the dosage form is then coated with another coating toprotect the formulation until it reaches the desired location, where themucoadhesive enables the formulation to be retained while thecomposition interacts with the target cell surface transport moiety.

Compositions disclosed herein can be administered to any organism, forexample an animal, preferably a mammal, bird, fish, insect, or arachnid.Preferred mammals include bovine, canine, equine, feline, ovine, andporcine animals, and non-human primates. Humans are particularlypreferred. Multiple techniques of administering or delivering a compoundexist in the art including, but not limited to, oral, rectal (e.g. anenema or suppository) aerosol (e.g., for nasal or pulmonary delivery),parenteral, and topical administration. Preferably, sufficientquantities of the biologically active peptide are delivered to achievethe intended effect. The particular amount of composition to bedelivered will depend on many factors, including the effect to beachieved, the type of organism to which the composition is delivered,delivery route, dosage regimen, and the age, health, and sex of theorganism. As such, the particular dosage of a composition incorporatedinto a given formulation is left to the ordinarily skilled artisan'sdiscretion.

Those skilled in the art will appreciate that when the compositionsdisclosed herein are administered as agents to achieve a particulardesired biological result, which may include a therapeutic, diagnostic,or protective effect(s) (including vaccination), it may be possible tocombine the minicell composition with a suitable pharmaceutical carrier.The choice of pharmaceutical carrier and the preparation of theminicells as a therapeutic or protective agent will depend on theintended use and mode of administration. Suitable formulations andmethods of administration of therapeutic agents include those for oral,pulmonary, nasal, buccal, ocular, dermal, rectal, intravenous, orvaginal delivery.

Depending on the mode of delivery employed, the context-dependentfunctional entity can be delivered in a variety of pharmaceuticallyacceptable forms. For example, the context-dependent functional entitycan be delivered in the form of a solid, solution, emulsion, dispersion,and the like, incorporated into a pill, capsule, tablet, suppository,aerosol, droplet, or spray. Pills, tablets, suppositories, aerosols,powders, droplets, and sprays may have complex, multilayer structuresand have a large range of sizes. Aerosols, powders, droplets, and spraysmay range from small (1 micron) to large (200 micron) in size.

Pharmaceutical compositions disclosed herein can be used in the form ofa solid, a lyophilized powder, a solution, an emulsion, a dispersion,and the like, wherein the resulting composition contains one or more ofthe compounds disclosed herein, as an active ingredient, in admixturewith an organic or inorganic carrier or excipient suitable for enteralor parenteral applications. The active ingredient may be compounded, forexample, with the usual non-toxic, pharmaceutically acceptable carriersfor tablets, pellets, capsules, suppositories, solutions, emulsions,suspensions, and any other form suitable for use. The carriers which canbe used include glucose, lactose, mannose, gum acacia, gelatin,mannitol, starch paste, magnesium trisilicate, talc, corn starch,keratin, colloidal silica, potato starch, urea, medium chain lengthtriglycerides, dextrans, and other carriers suitable for use inmanufacturing preparations, in solid, semisolid, or liquid form. Inaddition auxiliary, stabilizing, thickening and coloring agents andperfumes may be used. Examples of a stabilizing dry agent includetriulose, preferably at concentrations of 0.1% or greater (See, e.g.,U.S. Pat. No. 5,314,695). The active compound is included in thepharmaceutical composition in an amount sufficient to produce thedesired effect upon the process or condition of diseases.

6. Therapeutic Indications

The present disclosure relates to minicell-mediated immunotherapyagainst cancer(s) including but not limited to solid tumors, metastatictumors, and liquid tumors. Solid and metastatic tumors include those ofepithelial, fibroblast, muscle and bone origin and include but are notlimited to breast, lung, pancreatic, prostatic, testicular, ovarian,gastric, intestinal, mouth, tongue, pharynx, hepatic, anal, rectal,colonic, esophageal, urinary bladder, gall bladder, skin, uterine,vaginal, penal, and renal cancers. Other solid cancer types that may betreated with the immunomodulatory minicells disclosed herein include butare not limited to adenocarcinomas, sarcomas, fibrosarcomas, and cancersof the eye, brain, and bone. Liquid tumors that can be treated by theimmunomodulatory minicells disclosed herein include but are not limitedto non-Hodgkin's lymphoma, myeloma, Hodgkin's lymphoma, acutelymphocytic leukemia, chronic lymphocytic leukemia, acute myeloidleukemia, chronic myeloid leukemia, and other leukemias.

Immunomodulatory activities of VAX-P, VAX-IP, and VAX-IPD minicells invivo is shown in FIGS. 3-6 and as further described in Examples 2-4. Thefirst in vivo evidence that immunomodulatory effects are contributing tothe anti-tumor properties of perfringolysin O containing minicellformulations such as VAX-P, VAX-IP, and VAX-IPD minicells wasunexpected. In performing control experiments in the development and invivo characterization of VAX-IP, it was unexpectedly discovered that theremoval of the targeting moiety invasin had little to no effect on invivo efficacy (see FIG. 3). However, the removal of the perfringolysin Ocomponent had a marked effect on the ability of minicells to preventtumor growth. It was also unexpectedly discovered that minicells couldhave profound anti-tumor effects against tumors that had colonized theovaries of female mice, even though minicells were undetectable (i.e.did not localize) in ovaries (see FIGS. 4 & 5). In those same mice,tumors that had colonized the lung were also significantly preventedfrom growing and demonstrated ample minicell co-localization. Takentogether, these disparate results indicate that tumor localization maynot be critical for an anti-tumor effect and there is likely anotherglobal factor, likely to be some aspect of the immune system at play. Inaddition, it was demonstrated that minicells containing perfringolysin Ohad no effect on tumors grown in severely immune compromised NIH-IIImice (lack NK cell function in addition to T-cell function) (see FIG.6).

As a result of the immunomodulatory effect of minicells formulated asdescribed herein, one non-limiting yet preferred therapeutic applicationof the immunomodulatory minicells of the present invention is in theintravesical administration and treatment of non-muscle invasive bladdercancer. As shown in FIG. 7 and described in Example 5, immunodulatoryminicells have already demonstrated efficacy in a mouse model ofnon-muscle invasive bladder cancer.

7. Minicell Preparations

Some embodiments relate to creating an optimized strain and preparingimmunomodulatory minicells from, but not limited to, the bacterialfamily Enterobacteriaceae.

In some embodiments, the level of minicell producing viable parentalcell contamination is less than 1 in 10⁵ minicells. In some embodiments,the level of minicell producing viable parental cell contamination isless than 1 in 10⁶ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10⁷ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10⁸ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10⁹ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹⁰ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹¹ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹² minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹³ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹⁴ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹⁵ minicells.

In some embodiments, the level of minicell-producing viable parentalcell contamination is less than 1 in 10¹⁶ minicells.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. Although the present application has been described withreference to embodiments and examples, it should be understood thatvarious modifications can be made without departing from the spirit ofthe invention. All references cited herein are expressly incorporatedherein by reference in their entirety.

Embodiments of the present application are disclosed in further detailin the following examples, which are not in any way intended to limitthe scope of the present application.

EXAMPLES Example 1

Perfringolysin O is cytotoxic in vitro when targeted and delivered byVAX-IP minicells as demonstrated in Table 1 and FIG. 2. In vitroexperiments were performed by seeding 96-well plates with 25,000 murinetransitional cell carcinoma cell line MB49 in RPMI-1640 containing 10%fetal bovine serum, penicillin, and streptomycin. The following day,VAX-IP, VAX-I (containing no perfringolysin O), or recombinantperfringolysin O (BTX-100, purchased from ATCC) was added to cells at aratio of VAX-IP and VAX-I minicells added per plated mammalian (the MOI)of 1,000:1. The concentration of BTX-100 added was equivalent to theamount of perfringolysin O being delivered by VAX-IP. Initially, lactatedehydrogenase (LDH) activity assays were used as a surrogate readout ofcytotoxicity, primarily because LDH activity is a well known indicatorof mammalian cell membrane leakage, a mechanism by which perfringolysinO has been reported to act. As expected and as shown in FIG. 1, murinelactate dehydrogenase (LDH), was released from MB49 cells almostimmediately after exposure to BTX-100. MB49 cells treated with VAX-IP atan MOI of 1,000:1 also demonstrated LDH activity although the onset ofrelease was slower, likely due to the requirement for VAX-IP minicellinternalization, initiation of endosomal degradation, and eventualrelease of perfringolysin O into the target cell by way of endosomalmembrane break down, mediated by perfringolysin O. VAX-I minicells, usedas a control, demonstrated no significant release of LDH. Surprisingly,it was subsequently discovered that cells treated with BTX-100 hadrecovered by the 24 hr time point and were perfectly viable andadherent. On the other hand, those MB49 cells treated with VAX-IPminicells were detached from the plate and seemingly dead. To confirmthis result, the same experiment was repeated comparing a range ofVAX-IP minicells against a range of concentrations of BTX-100 but inthis instance a standard MTT cell viability assay was performed at the24 hr time point. The results of these experiments, shown in FIG. 2,clearly demonstrate that the intracellular delivery of a normallynon-toxic concentration of perfringolysin O can be quite potent whendelivered by minicells.

TABLE 1 mc to PFO MB49 PFO g/mc % LDH activity MOI at PFO g/mL mc/mL atg/mL at based on released from PFO g/mL 50% at 50% 50% RBC 50% RBChemolytic MB49 cells 2 hr for LDH MB49 MB49 lysis lysis assay after mcaddition activity viable viable BTX- NA 1.75 × 10⁻⁹ NA 87.8   5 × 10⁻⁷NA 1.07 × 10⁻⁶ 100 VAX-I No lysis NA 0 1.8 0 No NA toxicity VAX- 1.91 ×10⁶ NA 9.16 × 10⁻¹⁶ 94.0 2.29 × 10⁻⁷ 307.2 1.41 × 10⁻⁸ IP

Example 2

The first line of evidence that minicells containing perfringolysin Ostimulate anti-tumor immunomodulatory activity in vivo came from humanxenograft studies performed in athymic Nude mice (Nude mice arepartially immune compromised and lack a full complement of T-cellactivity). The anti-tumor efficacy of VAX-IP minicells when givenintravenously on a q3d schedule for a total of 6 doses was demonstratedin a subcutaneous xenograft study using the human pancreatic carcinomacell line BxPC3 (see FIG. 3). In this model, tumor cells were implantedsubcutaneously in Nude mice and allowed to reach a size of 100 mm³before being randomized into treatment groups. Tumor bearing mice weretreated intravenously on a q3d schedule for 6 total doses with eithersaline vehicle, paclitaxel, 3.0×10⁸ “naked” minicells (E. coli minicellscontaining no Invasin or perfringolysin O), 3.0×10⁸ VAX-P minicells(containing no Invasin protein on the minicell surface), or 3.0×10⁸VAX-IP minicells. Surprisingly, the non-targeted control group, VAX-Pminicells (containing no Invasin protein on the minicell surface), wasequally effective as VAX-IP minicells at preventing tumor growth in thismodel while “naked” minicells were ineffective. Anti-tumor activity inthe absence of a tumor targeting moiety on the surface of the minicellvehicle was completely unexpected.

Example 3

The second line of evidence that minicells containing perfringolysin Ostimulate anti-tumor immunomodulatory activity in vivo came from asyngeneic murine model of pulmonary and ovarian metastasis using theB16F10 murine melanoma cell line. In this model, B16F10 murine melanomacells that constitutively express firefly luciferase were injectedintravenously by tail vein into female Nude mice. Mice were injectedonce every 3 days with luciferin and animals imaged by whole mouseimaging for the presence of established metastases in the lungs of mice.Once tumor establishment was verified, mice were randomized into controlgroups and received either saline vehicle or 3.0×10⁸ VAX-IPD minicellsintravenously on a qd3 dosing schedule for a total of 6 doses.Significant anti-tumor activity against lung and ovarian metastases wasobserved in VAX-IPD minicells treated mice (see FIG. 4). In a second andparallel quantitative VAX-IPD plasmid specific PCR-based biodistributionstudy using the same model and dosing schedule, we determined thatVAX-IPD localized to the lungs and lung tumors in mice. Surprisingly, atno time point tested, was VAX-IPD minicells localized to the ovaries orovary tumors (see FIG. 5). From the combination of these two results, itwas concluded that some global factor, likely to be one or more immunefactors, must be contributing to anti-tumor activity if VAX-IPDminicells was not localizing to ovarian tissue or tumor but having aprofound tumor suppressive effects at that organ site.

Example 4

Based on the observations of the in vivo experiments performed inExamples 2 and 3, above, a third study was performed using anestablished subcutaneous tumor variation of the syngeneic B16F10 murinemelanoma model comparing anti-tumor efficacy of VAX-IPD minicells infully immune competent C57/BL6 mice to anti-tumor activity in severelyimmune deficient NIH-III mice (same genetic background as C57/BL6 butlacking both T-cell and Natural Killer cell activity). After tumors hadgrown to a size of 100 mm³, mice were randomized into treatment groupsand treated with either saline or 3.0×10⁸ VAX-IPD minicellsintravenously on a q3d schedule for a total of 6 doses. Following thefinal dose, mice were euthanized, tumors surgically extracted, weighed,and scored for tumor burden. The results, shown in FIG. 6, demonstratethat VAX-IPD minicells is ineffective in severely immune compromisedmice.

Example 5

The ability of VAX-IP minicells to work in a mouse model of non-muscleinvasive bladder cancer is demonstrated in FIG. 7. In this experiment,immune competent female C57/BL6 mice were anesthetized, subjected tocatheterization of the urinary bladder and their urinary bladder wallscauterized at two distinct sites using an electrosurgical device (Bovie940, set at 5 W) attached to a platinum guide wire and inserted throughthe catheter. Following cauterization, bladders were rinsed with 50 uLof PBS and then 100,000 MB49 murine transitional cell carcinoma tumorcells were instilled through the catheter. The catheter was locked inplace for 2 hr to ensure tumor adherence to the bladder wall. Catheterswere removed and animals were allowed to recover from anesthesia.Animals were monitored daily by bladder palpation until tumors could bedetected, at which time they were randomized into treatment groups. Micethen received an intravesical administration of either saline, 5×10⁷VAX-IP minicells, or 1×10⁸ VAX-IP minicells through a urinary catheteron a q3d schedule for a total of 5 doses. Animals were then euthanized,and bladders excised, weighed and scored for tumor burden. The resultsdemonstrate a strong dose-dependent anti-tumor effect of VAX-IPminicells against established MB49 urinary bladder carcinoma in thismodel.

Example 6

The production of VAX-IP minicells begins with the cloning of plasmidpVX-336 (SEQ ID NO. 3). pVX-336 (plasmid map shown in FIG. 9) wasconstructed by directionally subcloning Invasin into the SalI and XbaIsite of the L-rhamnose inducible plasmid pVX-128 (SEQ ID NO. 4, plasmidmap shown in FIG. 10). After the identification of positive clones, asubsequent directional subcloning of perfringolysin O into the uniqueXbaI and BamHI sites was conducted to create a transcriptional fusionbetween Invasin and perfringolysin O (a single prokaryotic message RNAcoding for two proteins, invasin and perfringolysin O). Followingpositive sequence identification of pVX-336, the plasmid was introducedinto an IPTG-inducible minicell-producing strain of E. coli (see Step 1of schematic in FIG. 8 and actual strain producing minicells uponinduction with IPTG in FIG. 11). The strain also contains a chromosomalcopy of a thermo-inducible I-ceuI suicide gene, a deletion in the dapAgene (rendering parental strain unable to grow outside of the laboratoryor in mammals), and a deletion in the lpxM gene (attenuates Lipid Acomponent of lipopolysaccharide). After introduction of the plasmid andselection on LB agar containing 10 ug/mL diaminopimelic acid and 50ug/mL kanamycin, a single colony is used to start an overnight culturegrown at 30° C. in liquid LB media containing the same. The followingday, the starter culture is diluted 1/100 into 3 L of fresh LB mediacontaining 10 ug/mL diaminopimelic acid and 50 ug/mL kanamycin and grownat 30° C. while shaking. Culture turbidity is monitored by OpticalDensity 600 (OD 600). At an OD 600 of 0.1, the culture is induced toexpress Invasin and perfringolysin O from pVX-336 by the addition ofL-rhamnose to a final concentration of 90 uM. At an OD 600 of 1.0, theculture is induced for VAX-IP minicell formation by the addition of IPTGto a final concentration of 100 uM. The culture is allowed to grow intostationary phase overnight and the following day VAX-IP minicells arepurified using a combination of differential centrifugation stepsfollowed by density gradient purification as is standard in the art.Once purified, minicells are tested for PFO content and activity by wayof red blood cell hemolysis assay as well as for the presence of Invasinby Western blot (see FIG. 12 for hemolysis assay and Western blot), theprimary detection antibody for which is a mouse monoclonal IgG2b(mAb3A2) specific for Invasin. The red blood cell hemolytic assay isperformed by lysing VAX-IP minicells with a combination of 2 mM EDTA, 10ug/mL lysozyme, an 5 mM cysteine, followed by and osmotic shock with icecold distilled water. Once lysed, lysates are quantified for proteincontent and the appropriate amounts added to 100,000 sheep red bloodcells in a 96 well plate. Plates are incubated at 37° C. with vigorousshaking for 1 hr. Following the 1 hr incubation time, red blood cellsare centrifuged down at 1,000×G for 5 min, and the supernatants moved toa new 96 well plate for analysis of hemoglobin release as a measure ofhemolytic activity at a wavelength of 541 nm

1. (canceled)
 2. (canceled)
 3. A bacterial minicell, comprisingperfringolysin O and invasin.
 4. The bacterial minicell of claim 3,wherein the invasin is from Yersinia pseudotuberculosis.
 5. Thebacterial minicell of claim 3, further comprising an exogenouspolypeptide that is not a protein toxin.
 6. The bacterial minicell ofclaim 3, further comprising a protein toxin.
 7. The bacterial minicellof claim 6, wherein the protein toxin is a catalytic fragment ofdiphtheria toxin, gelonin, Pseudomonas exotoxin A, or ricin A.
 8. Thebacterial minicell of claim 3, wherein the minicell is a Th1immunomodulatory minicell.
 9. The bacterial minicell of claim 3, whereinthe bacterial minicell is derived from a minicell-producing parentalbacterial cell with an inactivated lpxM gene.
 10. The bacterial minicellof claim 9, wherein the minicell is produced from a minicell-producingstrain of Salmonella spp., Listeria spp., Mycobacterium spp., Shigellaspp., Yersinia spp., or Escherichia coli.
 11. The bacterial minicell ofclaim 10, further comprising one or more Th1 cytokines, one or more poreforming cytolysin proteins, one or more phospholipases, or one or moreimmunomodulatory nucleic acids.
 12. The bacterial minicell of claim 11,wherein at least one of the one Th1 cytokines is IL-2, GMCSF, IL-12p40,IL-12p70, IL-18, TNF-α, or IFN-γ.
 13. A method of treating bladdercancer, comprising administering to a patient in need thereof abacterial minicell, wherein the bacterial minicell comprisesperfringolysin O and invasin.
 14. The method of claim 14, wherein thebladder cancer is non-muscle invasive bladder cancer.